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  68. </head>
    69. 

  69. <body>
    70. 

  70. 

  71.   <div class="container">
    72. 

  72. 

  73.     <h1>Underscore.js</h1>
    74. 

  74. 

  75.     <p>
    76. 

  76.       <a href="http://github.com/documentcloud/underscore/">Underscore</a> is a
    77. 

  77.       utility-belt library for JavaScript that provides a lot of the
    78. 

  78.       functional programming support that you would expect in
    79. 

  79.       <a href="http://prototypejs.org/api">Prototype.js</a>
    80. 

  80.       (or <a href="http://www.ruby-doc.org/core/classes/Enumerable.html">Ruby</a>),
    81. 

  81.       but without extending any of the built-in JavaScript objects. It's the
    82. 

  82.       tie to go along with <a href="http://docs.jquery.com">jQuery</a>'s tux.
    83. 

  83.     </p>
    84. 

  84. 

  85.     <p>
    86. 

  86.       Underscore provides 60-odd functions that support both the usual
    87. 

  87.       functional suspects: <b>map</b>, <b>select</b>, <b>invoke</b> &mdash;
    88. 

  88.       as well as more specialized helpers: function binding, javascript
    89. 

  89.       templating, deep equality testing, and so on. It delegates to built-in
    90. 

  90.       functions, if present, so modern browsers will use the
    91. 

  91.       native implementations of <b>forEach</b>, <b>map</b>, <b>reduce</b>,
    92. 

  92.       <b>filter</b>, <b>every</b>, <b>some</b> and <b>indexOf</b>.
    93. 

  93.     </p>
    94. 

  94. 

  95.     <p>
    96. 

  96.       A complete <a href="test/test.html">Test &amp; Benchmark Suite</a>
    97. 

  97.       is included for your perusal.
    98. 

  98.     </p>
    99. 

  99. 

  100.     <p>
    101. 

  101.       The unabridged source code is
    102. 

  102.       <a href="http://github.com/documentcloud/underscore/">available on GitHub</a>.
    103. 

  103.     </p>
    104. 

  104. 

  105.     <p>
    106. 

  106.       <i>Underscore is an open-source component of <a href="http://documentcloud.org/">DocumentCloud</a>.</i>
    107. 

  107.     </p>
    108. 

  108. 

  109.     <h2>Downloads <i style="padding-left: 12px; font-size:12px;">(Right-click, and use "Save As")</i></h2>
    110. 

  110. 

  111.     <p>
    112. 

  112.       <table>
    113. 

  113.         <tr>
    114. 

  114.           <td><a href="underscore.js">Development Version (0.6.0)</a></td>
    115. 

  115.           <td><i>25kb, Uncompressed with Comments</i></td>
    116. 

  116.         </tr>
    117. 

  117.         <tr>
    118. 

  118.           <td><a href="underscore-min.js">Production Version (0.6.0)</a></td>
    119. 

  119.           <td><i>3kb, Packed and Gzipped</i></td>
    120. 

  120.         </tr>
    121. 

  121.       </table>
    122. 

  122.     </p>
    123. 

  123. 

  124.     <h2>Table of Contents</h2>
    125. 

  125.     
    126. 

  126.     <a href="#styles">Object-Oriented and Functional Styles</a>
    127. 

  127. 

  128.     <p>
    129. 

  129.       <b>Collections</b>
    130. 

  130.       <br />
    131. 

  131.       <span class="methods"><a href="#each">each</a>, <a href="#map">map</a>,
    132. 

  132.       <a href="#reduce">reduce</a>, <a href="#reduceRight">reduceRight</a>,
    133. 

  133.       <a href="#detect">detect</a>, <a href="#select">select</a>,
    134. 

  134.       <a href="#reject">reject</a>, <a href="#all">all</a>,
    135. 

  135.       <a href="#any">any</a>, <a href="#include">include</a>,
    136. 

  136.       <a href="#invoke">invoke</a>, <a href="#pluck">pluck</a>,
    137. 

  137.       <a href="#max">max</a>, <a href="#min">min</a>,
    138. 

  138.       <a href="#sortBy">sortBy</a>, <a href="#sortedIndex">sortedIndex</a>,
    139. 

  139.       <a href="#toArray">toArray</a>, <a href="#size">size</a></span>
    140. 

  140.     </p>
    141. 

  141. 

  142.     <p>
    143. 

  143.       <b>Arrays</b>
    144. 

  144.       <br />
    145. 

  145.       <span class="methods"><a href="#first">first</a>, <a href="#rest">rest</a>, <a href="#last">last</a>,
    146. 

  146.       <a href="#compact">compact</a>, <a href="#flatten">flatten</a>, <a href="#without">without</a>, <a href="#uniq">uniq</a>,
    147. 

  147.       <a href="#intersect">intersect</a>, <a href="#zip">zip</a>, <a href="#indexOf">indexOf</a></span>,
    148. 

  148.       <a href="#lastIndexOf">lastIndexOf</a>, <a href="#range">range</a></span>
    149. 

  149.     </p>
    150. 

  150. 

  151.     <p>
    152. 

  152.       <b>Functions</b>
    153. 

  153.       <br />
    154. 

  154.       <span class="methods"><a href="#bind">bind</a>, <a href="#bindAll">bindAll</a>, <a href="#delay">delay</a>,
    155. 

  155.       <a href="#defer">defer</a>, <a href="#wrap">wrap</a></span>, <a href="#compose">compose</a></span>
    156. 

  156.     </p>
    157. 

  157. 

  158.     <p>
    159. 

  159.       <b>Objects</b>
    160. 

  160.       <br />
    161. 

  161.       <span class="methods"><a href="#keys">keys</a>, <a href="#values">values</a>,
    162. 

  162.       <a href="#functions">functions</a>, <a href="#extend">extend</a>, <a href="#clone">clone</a>, <a href="#tap">tap</a>,
    163. 

  163.       <a href="#isEqual">isEqual</a>, <a href="#isEmpty">isEmpty</a>, <a href="#isElement">isElement</a>,
    164. 

  164.       <a href="#isArray">isArray</a>, <a href="#isArguments">isArguments</a>, <a href="#isFunction">isFunction</a>, <a href="#isString">isString</a>,
    165. 

  165.       <a href="#isNumber">isNumber</a>, <a href="#isBoolean">isBoolean</a>, <a href="#isDate">isDate</a>, <a href="#isRegExp">isRegExp</a>
    166. 

  166.       <a href="#isNaN">isNaN</a>, <a href="#isNull">isNull</a>,
    167. 

  167.       <a href="#isUndefined">isUndefined</a>
    168. 

  168.       </span>
    169. 

  169.     </p>
    170. 

  170. 

  171.     <p>
    172. 

  172.       <b>Utility</b>
    173. 

  173.       <br />
    174. 

  174.       <span class="methods"><a href="#noConflict">noConflict</a>,
    175. 

  175.       <a href="#identity">identity</a>, <a href="#times">times</a>, 
    176. 

  176.       <a href="#breakLoop">breakLoop</a></span>, <a href="#mixin">mixin</a></span>, 
    177. 

  177.       <a href="#uniqueId">uniqueId</a>, <a href="#template">template</a></span>
    178. 

  178.     </p>
    179. 

  179. 

  180.     <p>
    181. 

  181.       <b>Chaining</b>
    182. 

  182.       <br />
    183. 

  183.       <span class="methods"><a href="#chain">chain</a>, <a href="#value">value</a>
    184. 

  184.     </p>
    185. 

  185. 

  186.     <div id="documentation">
    187. 

  187.       
    188. 

  188.       <h2 id="styles">Object-Oriented and Functional Styles</h2>
    189. 

  189. 

  190.       <p>
    191. 

  191.         You can use Underscore in either an object-oriented or a functional style,
    192. 

  192.         depending on your preference. The following two lines of code are
    193. 

  193.         identical ways to double a list of numbers.
    194. 

  194.       </p>
    195. 

  195. 

  196.     <pre>
    197. 

  197. _.map([1, 2, 3], function(n){ return n * 2; });
    198. 

  198. _([1, 2, 3]).map(function(n){ return n * 2; });</pre>
    199. 

  199. 

  200.       <p>
    201. 

  201.         Using the object-oriented style allows you to chain together methods. Calling
    202. 

  202.         <tt>chain</tt> on a wrapped object will cause all future method calls to
    203. 

  203.         return wrapped objects as well. When you've finished the computation,
    204. 

  204.         use <tt>value</tt> to retrieve the final value. Here's an example of chaining
    205. 

  205.         together a <b>map/flatten/reduce</b>, in order to get the word count of
    206. 

  206.         every word in a song.
    207. 

  207.       </p>
    208. 

  208. 

  209. <pre>
    210. 

  210. var lyrics = [
    211. 

  211.   {line : 1, words : "I'm a lumberjack and I'm okay"},
    212. 

  212.   {line : 2, words : "I sleep all night and I work all day"},
    213. 

  213.   {line : 3, words : "He's a lumberjack and he's okay"},
    214. 

  214.   {line : 4, words : "He sleeps all night and he works all day"}
    215. 

  215. ];
    216. 

  216. 

  217. _(lyrics).chain()
    218. 

  218.   .map(function(line) { return line.words.split(' '); })
    219. 

  219.   .flatten()
    220. 

  220.   .reduce({}, function(counts, word) {
    221. 

  221.     counts[word] = (counts[word] || 0) + 1;
    222. 

  222.     return counts;
    223. 

  223. }).value();
    224. 

  224. 

  225. =&gt; {lumberjack : 2, all : 4, night : 2 ... }</pre>
    226. 

  226. 

  227.       <p>
    228. 

  228.         In addition, the
    229. 

  229.         <a href="https://developer.mozilla.org/En/Core_JavaScript_1.5_Reference/Objects/Array">Array prototype's methods</a>
    230. 

  230.         are proxied through the chained Underscore object, so you can slip a
    231. 

  231.         <tt>reverse</tt> or a <tt>push</tt> into your chain, and continue to
    232. 

  232.         modify the array.
    233. 

  233.       </p>
    234. 

  234. 

  235.       <h2>Collection Functions (Arrays or Objects)</h2>
    236. 

  236. 

  237.       <p id="each">
    238. 

  238.         <b class="header">each</b><code>_.each(list, iterator, [context])</code>
    239. 

  239.         <span class="alias">Alias: <b>forEach</b></span>
    240. 

  240.         <br />
    241. 

  241.         Iterates over a <b>list</b> of elements, yielding each in turn to an <b>iterator</b>
    242. 

  242.         function. The <b>iterator</b> is bound to the <b>context</b> object, if one is
    243. 

  243.         passed. Each invocation of <b>iterator</b> is called with three arguments:
    244. 

  244.         <tt>(element, index, list)</tt>. If <b>list</b> is a JavaScript object, <b>iterator</b>'s
    245. 

  245.         arguments will be <tt>(value, key, list)</tt>. Use <a href="#breakLoop"><tt>breakLoop</tt></a>
    246. 

  246.         to break out of the iteration. Delegates to the native
    247. 

  247.         <b>forEach</b> function if it exists.
    248. 

  248.       </p>
    249. 

  249.       <pre>
    250. 

  250. _.each([1, 2, 3], function(num){ alert(num); });
    251. 

  251. =&gt; alerts each number in turn...</pre>
    252. 

  252. 

  253.       <p id="map">
    254. 

  254.         <b class="header">map</b><code>_.map(list, iterator, [context])</code>
    255. 

  255.         <br />
    256. 

  256.         Produces a new array of values by mapping each value in <b>list</b>
    257. 

  257.         through a transformation function (<b>iterator</b>). If the native
    258. 

  258.         <b>map</b> method exists, it will be used instead.
    259. 

  259.       </p>
    260. 

  260.       <pre>
    261. 

  261. _.map([1, 2, 3], function(num){ return num * 3 });
    262. 

  262. =&gt; [3, 6, 9]</pre>
    263. 

  263. 

  264.       <p id="reduce">
    265. 

  265.         <b class="header">reduce</b><code>_.reduce(list, memo, iterator, [context])</code>
    266. 

  266.         <span class="alias">Aliases: <b>inject, foldl</b></span>
    267. 

  267.         <br />
    268. 

  268.         Also known as <b>inject</b> and <b>foldl</b>, <b>reduce</b> boils down a
    269. 

  269.         <b>list</b> of values into a single value. <b>Memo</b> is the initial state
    270. 

  270.         of the reduction, and each successive step of it should be returned by
    271. 

  271.         <b>iterator</b>.
    272. 

  272.       </p>
    273. 

  273.       <pre>
    274. 

  274. var sum = _.reduce([1, 2, 3], 0, function(memo, num){ return memo + num });
    275. 

  275. =&gt; 6
    276. 

  276. </pre>
    277. 

  277. 

  278.       <p id="reduceRight">
    279. 

  279.         <b class="header">reduceRight</b><code>_.reduceRight(list, memo, iterator, [context])</code>
    280. 

  280.         <span class="alias">Alias: <b>foldr</b></span>
    281. 

  281.         <br />
    282. 

  282.         The right-associative version of <b>reduce</b>. Delegates to the
    283. 

  283.         JavaScript 1.8 version of <b>reduceRight</b>, if it exists. <b>Foldr</b>
    284. 

  284.         is not as useful in JavaScript as it would be in a language with lazy
    285. 

  285.         evaluation.
    286. 

  286.       </p>
    287. 

  287.       <pre>
    288. 

  288. var list = [[0, 1], [2, 3], [4, 5]];
    289. 

  289. var flat = _.reduceRight(list, [], function(a, b) { return a.concat(b); });
    290. 

  290. =&gt; [4, 5, 2, 3, 0, 1]
    291. 

  291. </pre>
    292. 

  292. 

  293.       <p id="detect">
    294. 

  294.         <b class="header">detect</b><code>_.detect(list, iterator, [context])</code>
    295. 

  295.         <br />
    296. 

  296.         Looks through each value in the <b>list</b>, returning the first one that
    297. 

  297.         passes a truth test (<b>iterator</b>). The function returns as
    298. 

  298.         soon as it finds an acceptable element, and doesn't traverse the
    299. 

  299.         entire list.
    300. 

  300.       </p>
    301. 

  301.       <pre>
    302. 

  302. var even = _.detect([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
    303. 

  303. =&gt; 2
    304. 

  304. </pre>
    305. 

  305. 

  306.       <p id="select">
    307. 

  307.         <b class="header">select</b><code>_.select(list, iterator, [context])</code>
    308. 

  308.         <span class="alias">Alias: <b>filter</b></span>
    309. 

  309.         <br />
    310. 

  310.         Looks through each value in the <b>list</b>, returning an array of all
    311. 

  311.         the values that pass a truth test (<b>iterator</b>). Delegates to the
    312. 

  312.         native <b>filter</b> method, if it exists.
    313. 

  313.       </p>
    314. 

  314.       <pre>
    315. 

  315. var evens = _.select([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
    316. 

  316. =&gt; [2, 4, 6]
    317. 

  317. </pre>
    318. 

  318. 

  319.       <p id="reject">
    320. 

  320.         <b class="header">reject</b><code>_.reject(list, iterator, [context])</code>
    321. 

  321.         <br />
    322. 

  322.         Returns the values in <b>list</b> without the elements that the truth
    323. 

  323.         test (<b>iterator</b>) passes. The opposite of <b>select</b>.
    324. 

  324.       </p>
    325. 

  325.       <pre>
    326. 

  326. var odds = _.reject([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
    327. 

  327. =&gt; [1, 3, 5]
    328. 

  328. </pre>
    329. 

  329. 

  330.       <p id="all">
    331. 

  331.         <b class="header">all</b><code>_.all(list, [iterator], [context])</code>
    332. 

  332.         <span class="alias">Alias: <b>every</b></span>
    333. 

  333.         <br />
    334. 

  334.         Returns <i>true</i> if all of the values in the <b>list</b> pass the <b>iterator</b>
    335. 

  335.         truth test. If an <b>iterator</b> is not provided, the truthy value of
    336. 

  336.         the element will be used instead. Delegates to the native method <b>every</b>, if
    337. 

  337.         present.
    338. 

  338.       </p>
    339. 

  339.       <pre>
    340. 

  340. _.all([true, 1, null, 'yes']);
    341. 

  341. =&gt; false
    342. 

  342. </pre>
    343. 

  343. 

  344.       <p id="any">
    345. 

  345.         <b class="header">any</b><code>_.any(list, [iterator], [context])</code>
    346. 

  346.         <span class="alias">Alias: <b>some</b></span>
    347. 

  347.         <br />
    348. 

  348.         Returns <i>true</i> if any of the values in the <b>list</b> pass the
    349. 

  349.         <b>iterator</b> truth test. Short-circuits and stops traversing the list
    350. 

  350.         if a true element is found. Delegates to the native method <b>some</b>,
    351. 

  351.         if present.
    352. 

  352.       </p>
    353. 

  353.       <pre>
    354. 

  354. _.any([null, 0, 'yes', false]);
    355. 

  355. =&gt; true
    356. 

  356. </pre>
    357. 

  357. 

  358.       <p id="include">
    359. 

  359.         <b class="header">include</b><code>_.include(list, value)</code>
    360. 

  360.         <br />
    361. 

  361.         Returns <i>true</i> if the <b>value</b> is present in the <b>list</b>, using
    362. 

  362.         <i>===</i> to test equality. Uses <b>indexOf</b> internally, if <b>list</b>
    363. 

  363.         is an Array.
    364. 

  364.       </p>
    365. 

  365.       <pre>
    366. 

  366. _.include([1, 2, 3], 3);
    367. 

  367. =&gt; true
    368. 

  368. </pre>
    369. 

  369. 

  370.       <p id="invoke">
    371. 

  371.         <b class="header">invoke</b><code>_.invoke(list, methodName, [*arguments])</code>
    372. 

  372.         <br />
    373. 

  373.         Calls the method named by <b>methodName</b> on each value in the <b>list</b>.
    374. 

  374.         Any extra arguments passed to <b>invoke</b> will be forwarded on to the
    375. 

  375.         method invocation.
    376. 

  376.       </p>
    377. 

  377.       <pre>
    378. 

  378. _.invoke([[5, 1, 7], [3, 2, 1]], 'sort');
    379. 

  379. =&gt; [[1, 5, 7], [1, 2, 3]]
    380. 

  380. </pre>
    381. 

  381. 

  382.       <p id="pluck">
    383. 

  383.         <b class="header">pluck</b><code>_.pluck(list, propertyName)</code>
    384. 

  384.         <br />
    385. 

  385.         An convenient version of what is perhaps the most common use-case for
    386. 

  386.         <b>map</b>: extracting a list of property values.
    387. 

  387.       </p>
    388. 

  388.       <pre>
    389. 

  389. var stooges = [{name : 'moe', age : 40}, {name : 'larry', age : 50}, {name : 'curly', age : 60}];
    390. 

  390. _.pluck(stooges, 'name');
    391. 

  391. =&gt; ["moe", "larry", "curly"]
    392. 

  392. </pre>
    393. 

  393. 

  394.       <p id="max">
    395. 

  395.         <b class="header">max</b><code>_.max(list, [iterator], [context])</code>
    396. 

  396.         <br />
    397. 

  397.         Returns the maximum value in <b>list</b>. If <b>iterator</b> is passed,
    398. 

  398.         it will be used on each value to generate the criterion by which the
    399. 

  399.         value is ranked.
    400. 

  400.       </p>
    401. 

  401.       <pre>
    402. 

  402. var stooges = [{name : 'moe', age : 40}, {name : 'larry', age : 50}, {name : 'curly', age : 60}];
    403. 

  403. _.max(stooges, function(stooge){ return stooge.age; });
    404. 

  404. =&gt; {name : 'curly', age : 60};
    405. 

  405. </pre>
    406. 

  406. 

  407.       <p id="min">
    408. 

  408.         <b class="header">min</b><code>_.min(list, [iterator], [context])</code>
    409. 

  409.         <br />
    410. 

  410.         Returns the minimum value in <b>list</b>. If <b>iterator</b> is passed,
    411. 

  411.         it will be used on each value to generate the criterion by which the
    412. 

  412.         value is ranked.
    413. 

  413.       </p>
    414. 

  414.       <pre>
    415. 

  415. var numbers = [10, 5, 100, 2, 1000];
    416. 

  416. _.min(numbers);
    417. 

  417. =&gt; 2
    418. 

  418. </pre>
    419. 

  419. 

  420.       <p id="sortBy">
    421. 

  421.         <b class="header">sortBy</b><code>_.sortBy(list, iterator, [context])</code>
    422. 

  422.         <br />
    423. 

  423.         Returns a sorted <b>list</b>, ranked by the results of running each
    424. 

  424.         value through <b>iterator</b>.
    425. 

  425.       </p>
    426. 

  426.       <pre>
    427. 

  427. _.sortBy([1, 2, 3, 4, 5, 6], function(num){ return Math.sin(num); });
    428. 

  428. =&gt; [5, 4, 6, 3, 1, 2]
    429. 

  429. </pre>
    430. 

  430. 

  431.       <p id="sortedIndex">
    432. 

  432.         <b class="header">sortedIndex</b><code>_.sortedIndex(list, value, [iterator])</code>
    433. 

  433.         <br />
    434. 

  434.         Uses a binary search to determine the index at which the <b>value</b>
    435. 

  435.         should be inserted into the <b>list</b> in order to maintain the <b>list</b>'s
    436. 

  436.         sorted order. If an <b>iterator</b> is passed, it will be used to compute
    437. 

  437.         the sort ranking of each value.
    438. 

  438.       </p>
    439. 

  439.       <pre>
    440. 

  440. _.sortedIndex([10, 20, 30, 40, 50], 35);
    441. 

  441. =&gt; 3
    442. 

  442. </pre>
    443. 

  443. 

  444.       <p id="toArray">
    445. 

  445.         <b class="header">toArray</b><code>_.toArray(list)</code>
    446. 

  446.         <br />
    447. 

  447.         Converts the <b>list</b> (anything that can be iterated over), into a
    448. 

  448.         real Array. Useful for transmuting the <b>arguments</b> object.
    449. 

  449.       </p>
    450. 

  450.       <pre>
    451. 

  451. (function(){ return _.toArray(arguments).slice(0); })(1, 2, 3);
    452. 

  452. =&gt; [1, 2, 3]
    453. 

  453. </pre>
    454. 

  454. 

  455.       <p id="size">
    456. 

  456.         <b class="header">size</b><code>_.size(list)</code>
    457. 

  457.         <br />
    458. 

  458.         Return the number of values in the <b>list</b>.
    459. 

  459.       </p>
    460. 

  460.       <pre>
    461. 

  461. _.size({one : 1, two : 2, three : 3});
    462. 

  462. =&gt; 3
    463. 

  463. </pre>
    464. 

  464. 

  465.       <h2>Array Functions</h2>
    466. 

  466. 

  467.       <p>
    468. 

  468.         <i>Note: All array functions will also work on the <b>arguments</b> object.</i>
    469. 

  469.       </p>
    470. 

  470. 

  471.       <p id="first">
    472. 

  472.         <b class="header">first</b><code>_.first(array, [n])</code>
    473. 

  473.         <span class="alias">Alias: <b>head</b></span>
    474. 

  474.         <br />
    475. 

  475.         Returns the first element of an <b>array</b>. Passing <b>n</b> will
    476. 

  476.         return the first <b>n</b> elements of the array.
    477. 

  477.       </p>
    478. 

  478.       <pre>
    479. 

  479. _.first([5, 4, 3, 2, 1]);
    480. 

  480. =&gt; 5
    481. 

  481. </pre>
    482. 

  482. 

  483.       <p id="rest">
    484. 

  484.         <b class="header">rest</b><code>_.rest(array, [index])</code>
    485. 

  485.         <span class="alias">Alias: <b>tail</b></span>
    486. 

  486.         <br />
    487. 

  487.         Returns the <b>rest</b> of the elements in an array. Pass an <b>index</b>
    488. 

  488.         to return the values of the array from that index onward.
    489. 

  489.       </p>
    490. 

  490.       <pre>
    491. 

  491. _.rest([5, 4, 3, 2, 1]);
    492. 

  492. =&gt; [4, 3, 2, 1]
    493. 

  493. </pre>
    494. 

  494. 

  495.       <p id="last">
    496. 

  496.         <b class="header">last</b><code>_.last(array)</code>
    497. 

  497.         <br />
    498. 

  498.         Returns the last element of an <b>array</b>.
    499. 

  499.       </p>
    500. 

  500.       <pre>
    501. 

  501. _.last([5, 4, 3, 2, 1]);
    502. 

  502. =&gt; 1
    503. 

  503. </pre>
    504. 

  504. 

  505.       <p id="compact">
    506. 

  506.         <b class="header">compact</b><code>_.compact(array)</code>
    507. 

  507.         <br />
    508. 

  508.         Returns a copy of the <b>array</b> with all falsy values removed.
    509. 

  509.         In JavaScript, <i>false</i>, <i>null</i>, <i>0</i>, <i>""</i>,
    510. 

  510.         <i>undefined</i> and <i>NaN</i> are all falsy.
    511. 

  511.       </p>
    512. 

  512.       <pre>
    513. 

  513. _.compact([0, 1, false, 2, '', 3]);
    514. 

  514. =&gt; [1, 2, 3]
    515. 

  515. </pre>
    516. 

  516. 

  517.       <p id="flatten">
    518. 

  518.         <b class="header">flatten</b><code>_.flatten(array)</code>
    519. 

  519.         <br />
    520. 

  520.         Flattens a nested <b>array</b> (the nesting can be to any depth).
    521. 

  521.       </p>
    522. 

  522.       <pre>
    523. 

  523. _.flatten([1, [2], [3, [[[4]]]]]);
    524. 

  524. =&gt; [1, 2, 3, 4];
    525. 

  525. </pre>
    526. 

  526. 

  527.       <p id="without">
    528. 

  528.         <b class="header">without</b><code>_.without(array, [*values])</code>
    529. 

  529.         <br />
    530. 

  530.         Returns a copy of the <b>array</b> with all instances of the <b>values</b>
    531. 

  531.         removed. <i>===</i> is used for the equality test.
    532. 

  532.       </p>
    533. 

  533.       <pre>
    534. 

  534. _.without([1, 2, 1, 0, 3, 1, 4], 0, 1);
    535. 

  535. =&gt; [2, 3, 4]
    536. 

  536. </pre>
    537. 

  537. 

  538.       <p id="uniq">
    539. 

  539.         <b class="header">uniq</b><code>_.uniq(array, [isSorted])</code>
    540. 

  540.         <br />
    541. 

  541.         Produces a duplicate-free version of the <b>array</b>, using <i>===</i> to test
    542. 

  542.         object equality. If you know in advance that the <b>array</b> is sorted,
    543. 

  543.         passing <i>true</i> for <b>isSorted</b> will run a much faster algorithm.
    544. 

  544.       </p>
    545. 

  545.       <pre>
    546. 

  546. _.uniq([1, 2, 1, 3, 1, 4]);
    547. 

  547. =&gt; [1, 2, 3, 4]
    548. 

  548. </pre>
    549. 

  549. 

  550.       <p id="intersect">
    551. 

  551.         <b class="header">intersect</b><code>_.intersect(*arrays)</code>
    552. 

  552.         <br />
    553. 

  553.         Computes the list of values that are the intersection of all the <b>arrays</b>.
    554. 

  554.         Each value in the result is present in each of the <b>arrays</b>.
    555. 

  555.       </p>
    556. 

  556.       <pre>
    557. 

  557. _.intersect([1, 2, 3], [101, 2, 1, 10], [2, 1]);
    558. 

  558. =&gt; [1, 2]
    559. 

  559. </pre>
    560. 

  560. 

  561.       <p id="zip">
    562. 

  562.         <b class="header">zip</b><code>_.zip(*arrays)</code>
    563. 

  563.         <br />
    564. 

  564.         Merges together the values of each of the <b>arrays</b> with the
    565. 

  565.         values at the corresponding position. Useful when you have separate
    566. 

  566.         data sources that are coordinated through matching array indexes.
    567. 

  567.       </p>
    568. 

  568.       <pre>
    569. 

  569. _.zip(['moe', 'larry', 'curly'], [30, 40, 50], [true, false, false]);
    570. 

  570. =&gt; [["moe", 30, true], ["larry", 40, false], ["curly", 50, false]]
    571. 

  571. </pre>
    572. 

  572. 

  573.       <p id="indexOf">
    574. 

  574.         <b class="header">indexOf</b><code>_.indexOf(array, value)</code>
    575. 

  575.         <br />
    576. 

  576.         Returns the index at which <b>value</b> can be found in the <b>array</b>,
    577. 

  577.         or <i>-1</i> if value is not present in the <b>array</b>. Uses the native
    578. 

  578.         <b>indexOf</b> function unless it's missing.
    579. 

  579.       </p>
    580. 

  580.       <pre>
    581. 

  581. _.indexOf([1, 2, 3], 2);
    582. 

  582. =&gt; 1
    583. 

  583. </pre>
    584. 

  584. 

  585.       <p id="lastIndexOf">
    586. 

  586.         <b class="header">lastIndexOf</b><code>_.lastIndexOf(array, value)</code>
    587. 

  587.         <br />
    588. 

  588.         Returns the index of the last occurrence of <b>value</b> in the <b>array</b>,
    589. 

  589.         or <i>-1</i> if value is not present. Uses the native <b>lastIndexOf</b>
    590. 

  590.         function if possible.
    591. 

  591.       </p>
    592. 

  592.       <pre>
    593. 

  593. _.lastIndexOf([1, 2, 3, 1, 2, 3], 2);
    594. 

  594. =&gt; 4
    595. 

  595. </pre>
    596. 

  596. 

  597.       <p id="range">
    598. 

  598.         <b class="header">range</b><code>_.range([start], stop, [step])</code>
    599. 

  599.         <br />
    600. 

  600.         A function to create flexibly-numbered lists of integers, handy for
    601. 

  601.         <tt>each</tt> and <tt>map</tt> loops. <b>start</b>, if omitted, defaults
    602. 

  602.         to <i>0</i>; <b>step</b> defaults to <i>1</i>. Returns a list of integers
    603. 

  603.         from <b>start</b> to <b>stop</b>, incremented (or decremented) by <b>step</b>,
    604. 

  604.         exclusive.
    605. 

  605.       </p>
    606. 

  606.       <pre>
    607. 

  607. _.range(10);
    608. 

  608. =&gt; [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    609. 

  609. _.range(1, 11);
    610. 

  610. =&gt; [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    611. 

  611. _.range(0, 30, 5);
    612. 

  612. =&gt; [0, 5, 10, 15, 20, 25]
    613. 

  613. _.range(0, -10, -1);
    614. 

  614. =&gt; [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
    615. 

  615. _.range(0);
    616. 

  616. =&gt; []
    617. 

  617. </pre>
    618. 

  618. 

  619.       <h2>Function (uh, ahem) Functions</h2>
    620. 

  620. 

  621.       <p id="bind">
    622. 

  622.         <b class="header">bind</b><code>_.bind(function, object, [*arguments])</code>
    623. 

  623.         <br />
    624. 

  624.         Bind a <b>function</b> to an <b>object</b>, meaning that whenever
    625. 

  625.         the function is called, the value of <i>this</i> will be the <b>object</b>.
    626. 

  626.         Optionally, bind <b>arguments</b> to the <b>function</b> to pre-fill them,
    627. 

  627.         also known as <b>currying</b>.
    628. 

  628.       </p>
    629. 

  629.       <pre>
    630. 

  630. var func = function(greeting){ return greeting + ': ' + this.name };
    631. 

  631. func = _.bind(func, {name : 'moe'}, 'hi');
    632. 

  632. func();
    633. 

  633. =&gt; 'hi: moe'
    634. 

  634. </pre>
    635. 

  635. 

  636.       <p id="bindAll">
    637. 

  637.         <b class="header">bindAll</b><code>_.bindAll(object, [*methodNames])</code>
    638. 

  638.         <br />
    639. 

  639.         Binds a number of methods on the <b>object</b>, specified by
    640. 

  640.         <b>methodNames</b>, to be run in the context of that object whenever they
    641. 

  641.         are invoked. Very handy for binding functions that are going to be used
    642. 

  642.         as event handlers, which would otherwise be invoked with a fairly useless
    643. 

  643.         <i>this</i>. If no <b>methodNames</b> are provided, all of the object's
    644. 

  644.         function properties will be bound to it.
    645. 

  645.       </p>
    646. 

  646.       <pre>
    647. 

  647. var buttonView = {
    648. 

  648.   label   : 'underscore',
    649. 

  649.   onClick : function(){ alert('clicked: ' + this.label); },
    650. 

  650.   onHover : function(){ console.log('hovering: ' + this.label); }
    651. 

  651. };
    652. 

  652. _.bindAll(buttonView);
    653. 

  653. jQuery('#underscore_button').bind('click', buttonView.onClick);
    654. 

  654. =&gt; When the button is clicked, this.label will have the correct value...
    655. 

  655. </pre>
    656. 

  656. 

  657.       <p id="delay">
    658. 

  658.         <b class="header">delay</b><code>_.delay(function, wait, [*arguments])</code>
    659. 

  659.         <br />
    660. 

  660.         Much like <b>setTimeout</b>, invokes <b>function</b> after <b>wait</b>
    661. 

  661.         milliseconds. If you pass the optional <b>arguments</b>, they will be
    662. 

  662.         forwarded on to the <b>function</b> when it is invoked.
    663. 

  663.       </p>
    664. 

  664.       <pre>
    665. 

  665. var log = _.bind(console.log, console);
    666. 

  666. _.delay(log, 1000, 'logged later');
    667. 

  667. =&gt; 'logged later' // Appears after one second.
    668. 

  668. </pre>
    669. 

  669. 

  670.       <p id="defer">
    671. 

  671.         <b class="header">defer</b><code>_.defer(function)</code>
    672. 

  672.         <br />
    673. 

  673.         Defers invoking the <b>function</b> until the current call stack has cleared,
    674. 

  674.         similar to using <b>setTimeout</b> with a delay of 0. Useful for performing
    675. 

  675.         expensive computations or HTML rendering in chunks without blocking the UI thread
    676. 

  676.         from updating.
    677. 

  677.       </p>
    678. 

  678.       <pre>
    679. 

  679. _.defer(function(){ alert('deferred'); });
    680. 

  680. // Returns from the function before the alert runs.
    681. 

  681. </pre>
    682. 

  682. 

  683.       <p id="wrap">
    684. 

  684.         <b class="header">wrap</b><code>_.wrap(function, wrapper)</code>
    685. 

  685.         <br />
    686. 

  686.         Wraps the first <b>function</b> inside of the <b>wrapper</b> function,
    687. 

  687.         passing it as the first argument. This allows the <b>wrapper</b> to
    688. 

  688.         execute code before and after the <b>function</b> runs, adjust the arguments,
    689. 

  689.         and execute it conditionally.
    690. 

  690.       </p>
    691. 

  691.       <pre>
    692. 

  692. var hello = function(name) { return "hello: " + name; };
    693. 

  693. hello = _.wrap(hello, function(func) {
    694. 

  694.   return "before, " + func("moe") + ", after";
    695. 

  695. });
    696. 

  696. hello();
    697. 

  697. =&gt; 'before, hello: moe, after'
    698. 

  698. </pre>
    699. 

  699. 

  700.       <p id="compose">
    701. 

  701.         <b class="header">compose</b><code>_.compose(*functions)</code>
    702. 

  702.         <br />
    703. 

  703.         Returns the composition of a list of <b>functions</b>, where each function
    704. 

  704.         consumes the return value of the function that follows. In math terms,
    705. 

  705.         composing the functions <i>f()</i>, <i>g()</i>, and <i>h()</i> produces
    706. 

  706.         <i>f(g(h()))</i>.
    707. 

  707.       </p>
    708. 

  708.       <pre>
    709. 

  709. var greet    = function(name){ return "hi: " + name; };
    710. 

  710. var exclaim  = function(statement){ return statement + "!"; };
    711. 

  711. var welcome = _.compose(greet, exclaim);
    712. 

  712. welcome('moe');
    713. 

  713. =&gt; 'hi: moe!'
    714. 

  714. </pre>
    715. 

  715. 

  716.       <h2>Object Functions</h2>
    717. 

  717. 

  718.       <p id="keys">
    719. 

  719.         <b class="header">keys</b><code>_.keys(object)</code>
    720. 

  720.         <br />
    721. 

  721.         Retrieve all the names of the <b>object</b>'s properties.
    722. 

  722.       </p>
    723. 

  723.       <pre>
    724. 

  724. _.keys({one : 1, two : 2, three : 3});
    725. 

  725. =&gt; ["one", "two", "three"]
    726. 

  726. </pre>
    727. 

  727. 

  728.       <p id="values">
    729. 

  729.         <b class="header">values</b><code>_.values(object)</code>
    730. 

  730.         <br />
    731. 

  731.         Return all of the values of the <b>object</b>'s properties.
    732. 

  732.       </p>
    733. 

  733.       <pre>
    734. 

  734. _.values({one : 1, two : 2, three : 3});
    735. 

  735. =&gt; [1, 2, 3]
    736. 

  736. </pre>
    737. 

  737. 

  738.       <p id="functions">
    739. 

  739.         <b class="header">functions</b><code>_.functions(object)</code>
    740. 

  740.         <span class="alias">Alias: <b>methods</b></span>
    741. 

  741.         <br />
    742. 

  742.         Returns a sorted list of the names of every method in an object &mdash;
    743. 

  743.         that is to say, the name of every function property of the object.
    744. 

  744.       </p>
    745. 

  745.       <pre>
    746. 

  746. _.functions(_);
    747. 

  747. =&gt; ["all", "any", "bind", "bindAll", "clone", "compact", "compose" ...
    748. 

  748. </pre>
    749. 

  749. 

  750.       <p id="extend">
    751. 

  751.         <b class="header">extend</b><code>_.extend(destination, source)</code>
    752. 

  752.         <br />
    753. 

  753.         Copy all of the properties in the <b>source</b> object over to the
    754. 

  754.         <b>destination</b> object.
    755. 

  755.       </p>
    756. 

  756.       <pre>
    757. 

  757. _.extend({name : 'moe'}, {age : 50});
    758. 

  758. =&gt; {name : 'moe', age : 50}
    759. 

  759. </pre>
    760. 

  760. 

  761.       <p id="clone">
    762. 

  762.         <b class="header">clone</b><code>_.clone(object)</code>
    763. 

  763.         <br />
    764. 

  764.         Create a shallow-copied clone of the <b>object</b>. Any nested objects
    765. 

  765.         or arrays will be copied by reference, not duplicated.
    766. 

  766.       </p>
    767. 

  767.       <pre>
    768. 

  768. _.clone({name : 'moe'});
    769. 

  769. =&gt; {name : 'moe'};
    770. 

  770. </pre>
    771. 

  771. 

  772.       <p id="tap">
    773. 

  773.         <b class="header">tap</b><code>_.tap(object, interceptor)</code>
    774. 

  774.         <br />
    775. 

  775.         Invokes <b>interceptor</b> with the <b>object</b>, and then returns <b>object</b>.
    776. 

  776.         The primary purpose of this method is to "tap into" a method chain, in order to perform operations on intermediate results within the chain.
    777. 

  777.       </p>
    778. 

  778.       <pre>
    779. 

  779. _([1,2,3,200]).chain().
    780. 

  780.   select(function(num) { return num % 2 == 0; }).
    781. 

  781.   tap(console.log).
    782. 

  782.   map(function(num) { return num * num }).
    783. 

  783.   value();
    784. 

  784. =&gt; [2, 200]
    785. 

  785. =&gt; [4, 40000]
    786. 

  786. </pre>
    787. 

  787. 

  788.       <p id="isEqual">
    789. 

  789.         <b class="header">isEqual</b><code>_.isEqual(object, other)</code>
    790. 

  790.         <br />
    791. 

  791.         Performs an optimized deep comparison between the two objects, to determine
    792. 

  792.         if they should be considered equal.
    793. 

  793.       </p>
    794. 

  794.       <pre>
    795. 

  795. var moe   = {name : 'moe', luckyNumbers : [13, 27, 34]};
    796. 

  796. var clone = {name : 'moe', luckyNumbers : [13, 27, 34]};
    797. 

  797. moe == clone;
    798. 

  798. =&gt; false
    799. 

  799. _.isEqual(moe, clone);
    800. 

  800. =&gt; true
    801. 

  801. </pre>
    802. 

  802. 

  803.       <p id="isEmpty">
    804. 

  804.         <b class="header">isEmpty</b><code>_.isEmpty(object)</code>
    805. 

  805.         <br />
    806. 

  806.         Returns <i>true</i> if <b>object</b> contains no values.
    807. 

  807.       </p>
    808. 

  808.       <pre>
    809. 

  809. _.isEmpty([1, 2, 3]);
    810. 

  810. =&gt; false
    811. 

  811. _.isEmpty({});
    812. 

  812. =&gt; true
    813. 

  813. </pre>
    814. 

  814. 

  815.       <p id="isElement">
    816. 

  816.         <b class="header">isElement</b><code>_.isElement(object)</code>
    817. 

  817.         <br />
    818. 

  818.         Returns <i>true</i> if <b>object</b> is a DOM element.
    819. 

  819.       </p>
    820. 

  820.       <pre>
    821. 

  821. _.isElement(jQuery('body')[0]);
    822. 

  822. =&gt; true
    823. 

  823. </pre>
    824. 

  824. 

  825.       <p id="isArray">
    826. 

  826.         <b class="header">isArray</b><code>_.isArray(object)</code>
    827. 

  827.         <br />
    828. 

  828.         Returns <i>true</i> if <b>object</b> is an Array.
    829. 

  829.       </p>
    830. 

  830.       <pre>
    831. 

  831. (function(){ return _.isArray(arguments); })();
    832. 

  832. =&gt; false
    833. 

  833. _.isArray([1,2,3]);
    834. 

  834. =&gt; true
    835. 

  835. </pre>
    836. 

  836. 

  837.       <p id="isArguments">
    838. 

  838.         <b class="header">isArguments</b><code>_.isArguments(object)</code>
    839. 

  839.         <br />
    840. 

  840.         Returns <i>true</i> if <b>object</b> is an Arguments object.
    841. 

  841.       </p>
    842. 

  842.       <pre>
    843. 

  843. (function(){ return _.isArguments(arguments); })(1, 2, 3);
    844. 

  844. =&gt; true
    845. 

  845. _.isArguments([1,2,3]);
    846. 

  846. =&gt; false
    847. 

  847. </pre>
    848. 

  848. 

  849.       <p id="isFunction">
    850. 

  850.         <b class="header">isFunction</b><code>_.isFunction(object)</code>
    851. 

  851.         <br />
    852. 

  852.         Returns <i>true</i> if <b>object</b> is a Function.
    853. 

  853.       </p>
    854. 

  854.       <pre>
    855. 

  855. _.isFunction(alert);
    856. 

  856. =&gt; true
    857. 

  857. </pre>
    858. 

  858. 

  859.       <p id="isString">
    860. 

  860.         <b class="header">isString</b><code>_.isString(object)</code>
    861. 

  861.         <br />
    862. 

  862.         Returns <i>true</i> if <b>object</b> is a String.
    863. 

  863.       </p>
    864. 

  864.       <pre>
    865. 

  865. _.isFunction("moe");
    866. 

  866. =&gt; true
    867. 

  867. </pre>
    868. 

  868. 

  869.       <p id="isNumber">
    870. 

  870.         <b class="header">isNumber</b><code>_.isNumber(object)</code>
    871. 

  871.         <br />
    872. 

  872.         Returns <i>true</i> if <b>object</b> is a Number.
    873. 

  873.       </p>
    874. 

  874.       <pre>
    875. 

  875. _.isNumber(8.4 * 5);
    876. 

  876. =&gt; true
    877. 

  877. </pre>
    878. 

  878. 

  879.       <p id="isBoolean">
    880. 

  880.         <b class="header">isBoolean</b><code>_.isBoolean(object)</code>
    881. 

  881.         <br />
    882. 

  882.         Returns <i>true</i> if <b>object</b> is either <i>true</i> or <i>false</i>.
    883. 

  883.       </p>
    884. 

  884.       <pre>
    885. 

  885. _.isBoolean(null);
    886. 

  886. =&gt; false
    887. 

  887. </pre>
    888. 

  888. 

  889.       <p id="isDate">
    890. 

  890.         <b class="header">isDate</b><code>_.isDate(object)</code>
    891. 

  891.         <br />
    892. 

  892.         Returns <i>true</i> if <b>object</b> is a Date.
    893. 

  893.       </p>
    894. 

  894.       <pre>
    895. 

  895. _.isDate(new Date());
    896. 

  896. =&gt; true
    897. 

  897. </pre>
    898. 

  898. 

  899.       <p id="isRegExp">
    900. 

  900.         <b class="header">isRegExp</b><code>_.isRegExp(object)</code>
    901. 

  901.         <br />
    902. 

  902.         Returns <i>true</i> if <b>object</b> is a RegExp.
    903. 

  903.       </p>
    904. 

  904.       <pre>
    905. 

  905. _.isRegExp(/moe/);
    906. 

  906. =&gt; true
    907. 

  907. </pre>
    908. 

  908. 

  909.       <p id="isNaN">
    910. 

  910.         <b class="header">isNaN</b><code>_.isNaN(object)</code>
    911. 

  911.         <br />
    912. 

  912.         Returns <i>true</i> if <b>object</b> is <i>NaN</i>.<br /> Note: this is not
    913. 

  913.         the same as the native <b>isNaN</b> function, which will also return
    914. 

  914.         true if the variable is <i>undefined</i>.
    915. 

  915.       </p>
    916. 

  916.       <pre>
    917. 

  917. _.isNaN(NaN);
    918. 

  918. =&gt; true
    919. 

  919. isNaN(undefined);
    920. 

  920. =&gt; true
    921. 

  921. _.isNaN(undefined);
    922. 

  922. =&gt; false
    923. 

  923. </pre>
    924. 

  924. 

  925.       <p id="isNull">
    926. 

  926.         <b class="header">isNull</b><code>_.isNull(object)</code>
    927. 

  927.         <br />
    928. 

  928.         Returns <i>true</i> if the value of <b>object</b> is <i>null</i>.
    929. 

  929.       </p>
    930. 

  930.       <pre>
    931. 

  931. _.isNull(null);
    932. 

  932. =&gt; true
    933. 

  933. _.isNull(undefined);
    934. 

  934. =&gt; false
    935. 

  935. </pre>
    936. 

  936. 

  937.       <p id="isUndefined">
    938. 

  938.         <b class="header">isUndefined</b><code>_.isUndefined(variable)</code>
    939. 

  939.         <br />
    940. 

  940.         Returns <i>true</i> if <b>variable</b> is <i>undefined</i>.
    941. 

  941.       </p>
    942. 

  942.       <pre>
    943. 

  943. _.isUndefined(window.missingVariable);
    944. 

  944. =&gt; true
    945. 

  945. </pre>
    946. 

  946. 

  947.       <h2>Utility Functions</h2>
    948. 

  948. 

  949.       <p id="noConflict">
    950. 

  950.         <b class="header">noConflict</b><code>_.noConflict()</code>
    951. 

  951.         <br />
    952. 

  952.         Give control of the "_" variable back to its previous owner. Returns
    953. 

  953.         a reference to the <b>Underscore</b> object.
    954. 

  954.       </p>
    955. 

  955.       <pre>
    956. 

  956. var underscore = _.noConflict();</pre>
    957. 

  957. 

  958.       <p id="identity">
    959. 

  959.         <b class="header">identity</b><code>_.identity(value)</code>
    960. 

  960.         <br />
    961. 

  961.         Returns the same value that is used as the argument. In math:
    962. 

  962.         <tt>f(x) = x</tt><br />
    963. 

  963.         This function looks useless, but is used throughout Underscore as
    964. 

  964.         a default iterator.
    965. 

  965.       </p>
    966. 

  966.       <pre>
    967. 

  967. var moe = {name : 'moe'};
    968. 

  968. moe === _.identity(moe);
    969. 

  969. =&gt; true</pre>
    970. 

  970. 

  971.       <p id="times">
    972. 

  972.         <b class="header">times</b><code>_.times(n, iterator)</code>
    973. 

  973.         <br />
    974. 

  974.         Invokes the given iterator function <b>n</b> times.
    975. 

  975.       </p>
    976. 

  976.       <pre>
    977. 

  977. _(3).times(function(){ genie.grantWish(); });</pre>
    978. 

  978. 

  979.       <p id="breakLoop">
    980. 

  980.         <b class="header">breakLoop</b><code>_.breakLoop()</code>
    981. 

  981.         <br />
    982. 

  982.         Breaks out of the current loop iteration. Similar to the <tt>break</tt>
    983. 

  983.         keyword in regular "for" loop, but works within an iterator function.
    984. 

  984.         Uses the native <tt>StopIteration</tt> object in JavaScript 1.7 compliant
    985. 

  985.         browsers.
    986. 

  986.       </p>
    987. 

  987.       <pre>
    988. 

  988. var result = null;
    989. 

  989. _.each([1, 2, 3], function(num) {
    990. 

  990.   if ((result = num) == 2) _.breakLoop();
    991. 

  991. });
    992. 

  992. result;
    993. 

  993. =&gt; 2</pre>
    994. 

  994. 

  995.       <p id="mixin">
    996. 

  996.         <b class="header">mixin</b><code>_.mixin(object)</code>
    997. 

  997.         <br />
    998. 

  998.         Allows you to extend Underscore with your own utility functions. Pass
    999. 

  999.         a hash of <tt>{name: function}</tt> definitions to have your functions 
    1000. 

  1000.         added to the Underscore object, as well as the OOP wrapper.
    1001. 

  1001.       </p>
    1002. 

  1002.       <pre>
    1003. 

  1003. _.mixin({
    1004. 

  1004.   capitalize : function(string) {
    1005. 

  1005.     return string.charAt(0).toUpperCase() + string.substring(1).toLowerCase();
    1006. 

  1006.   }
    1007. 

  1007. });
    1008. 

  1008. _("fabio").capitalize();
    1009. 

  1009. =&gt; "Fabio"
    1010. 

  1010. </pre>
    1011. 

  1011. 

  1012.       <p id="uniqueId">
    1013. 

  1013.         <b class="header">uniqueId</b><code>_.uniqueId([prefix])</code>
    1014. 

  1014.         <br />
    1015. 

  1015.         Generate a globally-unique id for client-side models or DOM elements
    1016. 

  1016.         that need one. If <b>prefix</b> is passed, the id will be appended to it.
    1017. 

  1017.       </p>
    1018. 

  1018.       <pre>
    1019. 

  1019. _.uniqueId('contact_');
    1020. 

  1020. =&gt; 'contact_104'</pre>
    1021. 

  1021. 

  1022.       <p id="template">
    1023. 

  1023.         <b class="header">template</b><code>_.template(templateString, [context])</code>
    1024. 

  1024.         <br />
    1025. 

  1025.         Compiles JavaScript templates into functions that can be evaluated
    1026. 

  1026.         for rendering. Useful for rendering complicated bits of HTML from JSON
    1027. 

  1027.         data sources. Template functions can both interpolate variables, using<br />
    1028. 

  1028.         <tt>&lt;%= &hellip; %&gt;</tt>, as well as execute arbitrary JavaScript code, with
    1029. 

  1029.         <tt>&lt;% &hellip; %&gt;</tt>. When you evaluate a template function, pass in a
    1030. 

  1030.         <b>context</b> object that has properties corresponding to the template's free
    1031. 

  1031.         variables. If you're writing a one-off, you can pass the <b>context</b>
    1032. 

  1032.         object as the second parameter to <b>template</b> in order to render
    1033. 

  1033.         immediately instead of returning a template function.
    1034. 

  1034.       </p>
    1035. 

  1035.       <pre>
    1036. 

  1036. var compiled = _.template("hello: &lt;%= name %&gt;");
    1037. 

  1037. compiled({name : 'moe'});
    1038. 

  1038. =&gt; "hello: moe"
    1039. 

  1039. 

  1040. var list = "&lt;% _.each(people, function(name) { %&gt; &lt;li&gt;&lt;%= name %&gt;&lt;/li&gt; &lt;% }); %&gt;";
    1041. 

  1041. _.template(list, {people : ['moe', 'curly', 'larry']});
    1042. 

  1042. =&gt; "&lt;li&gt;moe&lt;/li&gt;&lt;li&gt;curly&lt;/li&gt;&lt;li&gt;larry&lt;/li&gt;"</pre>
    1043. 

  1043. 

  1044.       <p>
    1045. 

  1045.         If ERB-style delimiters aren't your cup of tea, you can change Underscore's
    1046. 

  1046.         template settings to use different symbols to set off interpolated code.
    1047. 

  1047.         Define <b>start</b> and <b>end</b> tokens, and an <b>interpolate</b> regex
    1048. 

  1048.         to match expressions that should be evaluated and inserted. For example,
    1049. 

  1049.         to perform
    1050. 

  1050.         <a href="http://github.com/janl/mustache.js#readme">Mustache.js</a>
    1051. 

  1051.         style templating:
    1052. 

  1052.       </p>
    1053. 

  1053. 

  1054.       <pre>
    1055. 

  1055. _.templateSettings = {
    1056. 

  1056.   start       : '{{',
    1057. 

  1057.   end         : '}}',
    1058. 

  1058.   interpolate : /\{\{(.+?)\}\}/g
    1059. 

  1059. };
    1060. 

  1060. 

  1061. var template = _.template("Hello {{ name }}!");
    1062. 

  1062. template({name : "Mustache"});
    1063. 

  1063. =&gt; "Hello Mustache!"</pre>
    1064. 

  1064. 

  1065.       <h2>Chaining</h2>
    1066. 

  1066. 

  1067.       <p id="chain">
    1068. 

  1068.         <b class="header">chain</b><code>_(obj).chain()</code>
    1069. 

  1069.         <br />
    1070. 

  1070.         Returns a wrapped object. Calling methods on this object will continue
    1071. 

  1071.         to return wrapped objects until <tt>value</tt> is used. (
    1072. 

  1072.         <a href="#styles">A more realistic example.</a>)
    1073. 

  1073.       </p>
    1074. 

  1074.       <pre>
    1075. 

  1075. var stooges = [{name : 'curly', age : 25}, {name : 'moe', age : 21}, {name : 'larry', age : 23}];
    1076. 

  1076. var youngest = _(stooges).chain()
    1077. 

  1077.   .sortBy(function(stooge){ return stooge.age; })
    1078. 

  1078.   .map(function(stooge){ return stooge.name + ' is ' + stooge.age; })
    1079. 

  1079.   .first()
    1080. 

  1080.   .value();
    1081. 

  1081. =&gt; "moe is 21"
    1082. 

  1082. </pre>
    1083. 

  1083. 

  1084.       <p id="value">
    1085. 

  1085.         <b class="header">value</b><code>_(obj).value()</code>
    1086. 

  1086.         <br />
    1087. 

  1087.         Extracts the value of a wrapped object.
    1088. 

  1088.       </p>
    1089. 

  1089.       <pre>
    1090. 

  1090. _([1, 2, 3]).value();
    1091. 

  1091. =&gt; [1, 2, 3]
    1092. 

  1092. </pre>
    1093. 

  1093. 

  1094.       <h2 id="duck_typing">Duck Typing</h2>
    1095. 

  1095. 

  1096.       <p>
    1097. 

  1097.         The <b>isType</b> (<tt>isArray</tt>, <tt>isFunction</tt>, <tt>isString</tt> ...) family of type-checking
    1098. 

  1098.         functions use property detection to do their work, which, although
    1099. 

  1099.         orders of magnitude faster than the alternative, isn't entirely safe when dealing
    1100. 

  1100.         with objects that are used as hashes, where arbitrary strings are being
    1101. 

  1101.         set for the keys. It's entirely possible for an object to masquerade as
    1102. 

  1102.         another type, if you're setting properties with names like "concat" and
    1103. 

  1103.         "charCodeAt". So be aware.
    1104. 

  1104.       </p>
    1105. 

  1105. 

  1106. 

  1107.       <h2>Links &amp; Suggested Reading</h2>
    1108. 

  1108. 

  1109.       <p>
    1110. 

  1110.         <a href="http://mirven.github.com/underscore.lua/">Underscore.lua</a>,
    1111. 

  1111.         a Lua port of the functions that are applicable in both languages.
    1112. 

  1112.         Includes OOP-wrapping and chaining.
    1113. 

  1113.         The <a href="http://github.com/mirven/underscore.lua">source</a> is
    1114. 

  1114.         available on GitHub.
    1115. 

  1115.       </p>
    1116. 

  1116. 

  1117.       <p>
    1118. 

  1118.         Ruby's <a href="http://ruby-doc.org/core/classes/Enumerable.html">Enumerable</a> module.
    1119. 

  1119.       </p>
    1120. 

  1120. 

  1121.       <p>
    1122. 

  1122.         <a href="http://www.prototypejs.org/">Prototype.js</a>, which provides
    1123. 

  1123.         JavaScript with collection functions in the manner closest to Ruby's Enumerable.
    1124. 

  1124.       </p>
    1125. 

  1125. 

  1126.       <p>
    1127. 

  1127.         Oliver Steele's
    1128. 

  1128.         <a href="http://osteele.com/sources/javascript/functional/">Functional JavaScript</a>,
    1129. 

  1129.         which includes comprehensive higher-order function support as well as string lambdas.
    1130. 

  1130.       </p>
    1131. 

  1131. 

  1132.       <p>
    1133. 

  1133.         Python's <a href="http://docs.python.org/library/itertools.html">itertools</a>.
    1134. 

  1134.       </p>
    1135. 

  1135. 

  1136.       <h2>Change Log</h2>
    1137. 

  1137.       
    1138. 

  1138.       <p>
    1139. 

  1139.         <b class="header">0.6.0</b><br />
    1140. 

  1140.         Major release. Incorporates a number of 
    1141. 

  1141.         <a href="http://github.com/ratbeard">Mile Frawley's</a> refactors for
    1142. 

  1142.         safer duck-typing on collection functions, and cleaner internals. A new
    1143. 

  1143.         <tt>_.mixin</tt> method that allows you to extend Underscore with utility
    1144. 

  1144.         functions of your own. Added <tt>_.times</tt>, which works the same as in 
    1145. 

  1145.         Ruby or Prototype.js. Native support for ECMAScript 5's <tt>Array.isArray</tt>, 
    1146. 

  1146.         and <tt>Object.keys</tt>.
    1147. 

  1147.       </p>
    1148. 

  1148. 

  1149.       <p>
    1150. 

  1150.         <b class="header">0.5.8</b><br />
    1151. 

  1151.         Fixed Underscore's collection functions to work on
    1152. 

  1152.         <a href="https://developer.mozilla.org/En/DOM/NodeList">NodeLists</a> and
    1153. 

  1153.         <a href="https://developer.mozilla.org/En/DOM/HTMLCollection">HTMLCollections</a>
    1154. 

  1154.         once more, thanks to
    1155. 

  1155.         <a href="http://github.com/jmtulloss">Justin Tulloss</a>.
    1156. 

  1156.       </p>
    1157. 

  1157. 

  1158.       <p>
    1159. 

  1159.         <b class="header">0.5.7</b><br />
    1160. 

  1160.         A safer implementation of <tt>_.isArguments</tt>, and a
    1161. 

  1161.         faster <tt>_.isNumber</tt>,<br />thanks to
    1162. 

  1162.         <a href="http://jedschmidt.com/">Jed Schmidt</a>.
    1163. 

  1163.       </p>
    1164. 

  1164. 

  1165.       <p>
    1166. 

  1166.         <b class="header">0.5.6</b><br />
    1167. 

  1167.         Customizable delimiters for <tt>_.template</tt>, contributed by
    1168. 

  1168.         <a href="http://github.com/iamnoah">Noah Sloan</a>.
    1169. 

  1169.       </p>
    1170. 

  1170. 

  1171.       <p>
    1172. 

  1172.         <b class="header">0.5.5</b><br />
    1173. 

  1173.         Fix for a bug in MobileSafari's OOP-wrapper, with the arguments object.
    1174. 

  1174.       </p>
    1175. 

  1175. 

  1176.       <p>
    1177. 

  1177.         <b class="header">0.5.4</b><br />
    1178. 

  1178.         Fix for multiple single quotes within a template string for
    1179. 

  1179.         <tt>_.template</tt>. See:
    1180. 

  1180.         <a href="http://www.west-wind.com/Weblog/posts/509108.aspx">Rick Strahl's blog post</a>.
    1181. 

  1181.       </p>
    1182. 

  1182. 

  1183.       <p>
    1184. 

  1184.         <b class="header">0.5.2</b><br />
    1185. 

  1185.         New implementations of <tt>isArray</tt>, <tt>isDate</tt>, <tt>isFunction</tt>,
    1186. 

  1186.         <tt>isNumber</tt>, <tt>isRegExp</tt>, and <tt>isString</tt>, thanks to
    1187. 

  1187.         a suggestion from
    1188. 

  1188.         <a href="http://www.broofa.com/">Robert Kieffer</a>.
    1189. 

  1189.         Instead of doing <tt>Object#toString</tt>
    1190. 

  1190.         comparisons, they now check for expected properties, which is less safe,
    1191. 

  1191.         but more than an order of magnitude faster. Most other Underscore
    1192. 

  1192.         functions saw minor speed improvements as a result.
    1193. 

  1193.         <a href="http://dolzhenko.org/">Evgeniy Dolzhenko</a>
    1194. 

  1194.         contributed <tt>_.tap</tt>,
    1195. 

  1195.         <a href="http://ruby-doc.org/core-1.9/classes/Object.html#M000191">similar to Ruby 1.9's</a>,
    1196. 

  1196.         which is handy for injecting side effects (like logging) into chained calls.
    1197. 

  1197.       </p>
    1198. 

  1198. 

  1199.       <p>
    1200. 

  1200.         <b class="header">0.5.1</b><br />
    1201. 

  1201.         Added an <tt>_.isArguments</tt> function. Lots of little safety checks
    1202. 

  1202.         and optimizations contributed by
    1203. 

  1203.         <a href="http://github.com/iamnoah/">Noah Sloan</a> and Andri Möll.
    1204. 

  1204.       </p>
    1205. 

  1205. 

  1206.       <p>
    1207. 

  1207.         <b class="header">0.5.0</b><br />
    1208. 

  1208.         <b>[API Changes]</b> <tt>_.bindAll</tt> now takes the context object as
    1209. 

  1209.         its first parameter. If no method names are passed, all of the context
    1210. 

  1210.         object's methods are bound to it, enabling chaining and easier binding.
    1211. 

  1211.         <tt>_.functions</tt> now takes a single argument and returns the names
    1212. 

  1212.         of its Function properties. Calling <tt>_.functions(_)</tt> will get you
    1213. 

  1213.         the previous behavior.
    1214. 

  1214.         Added <tt>_.isRegExp</tt> so that <tt>isEqual</tt> can now test for RegExp equality.
    1215. 

  1215.         All of the "is" functions have been shrunk down into a single definition.
    1216. 

  1216.         <a href="http://github.com/grayrest/">Karl Guertin</a> contributed patches.
    1217. 

  1217.       </p>
    1218. 

  1218. 

  1219.       <p>
    1220. 

  1220.         <b class="header">0.4.7</b><br />
    1221. 

  1221.         Added <tt>isDate</tt>, <tt>isNaN</tt>, and <tt>isNull</tt>, for completeness.
    1222. 

  1222.         Optimizations for <tt>isEqual</tt> when checking equality between Arrays
    1223. 

  1223.         or Dates. <tt>_.keys</tt> is now <small><i><b>25%&ndash;2X</b></i></small> faster (depending on your
    1224. 

  1224.         browser) which speeds up the functions that rely on it, such as <tt>_.each</tt>.
    1225. 

  1225.       </p>
    1226. 

  1226. 

  1227.       <p>
    1228. 

  1228.         <b class="header">0.4.6</b><br />
    1229. 

  1229.         Added the <tt>range</tt> function, a port of the
    1230. 

  1230.         <a href="http://docs.python.org/library/functions.html#range">Python
    1231. 

  1231.         function of the same name</a>, for generating flexibly-numbered lists
    1232. 

  1232.         of integers. Original patch contributed by
    1233. 

  1233.         <a href="http://github.com/kylichuku">Kirill Ishanov</a>.
    1234. 

  1234.       </p>
    1235. 

  1235. 

  1236.       <p>
    1237. 

  1237.         <b class="header">0.4.5</b><br />
    1238. 

  1238.         Added <tt>rest</tt> for Arrays and arguments objects, and aliased
    1239. 

  1239.         <tt>first</tt> as <tt>head</tt>, and <tt>rest</tt> as <tt>tail</tt>,
    1240. 

  1240.         thanks to <a href="http://github.com/lukesutton/">Luke Sutton</a>'s patches.
    1241. 

  1241.         Added tests ensuring that all Underscore Array functions also work on
    1242. 

  1242.         <i>arguments</i> objects.
    1243. 

  1243.       </p>
    1244. 

  1244. 

  1245.       <p>
    1246. 

  1246.         <b class="header">0.4.4</b><br />
    1247. 

  1247.         Added <tt>isString</tt>, and <tt>isNumber</tt>, for consistency. Fixed
    1248. 

  1248.         <tt>_.isEqual(NaN, NaN)</tt> to return <i>true</i> (which is debatable).
    1249. 

  1249.       </p>
    1250. 

  1250. 

  1251.       <p>
    1252. 

  1252.         <b class="header">0.4.3</b><br />
    1253. 

  1253.         Started using the native <tt>StopIteration</tt> object in browsers that support it.
    1254. 

  1254.         Fixed Underscore setup for CommonJS environments.
    1255. 

  1255.       </p>
    1256. 

  1256. 

  1257.       <p>
    1258. 

  1258.         <b class="header">0.4.2</b><br />
    1259. 

  1259.         Renamed the unwrapping function to <tt>value</tt>, for clarity.
    1260. 

  1260.       </p>
    1261. 

  1261. 

  1262.       <p>
    1263. 

  1263.         <b class="header">0.4.1</b><br />
    1264. 

  1264.         Chained Underscore objects now support the Array prototype methods, so
    1265. 

  1265.         that you can perform the full range of operations on a wrapped array
    1266. 

  1266.         without having to break your chain. Added a <tt>breakLoop</tt> method
    1267. 

  1267.         to <b>break</b> in the middle of any Underscore iteration. Added an
    1268. 

  1268.         <tt>isEmpty</tt> function that works on arrays and objects.
    1269. 

  1269.       </p>
    1270. 

  1270. 

  1271.       <p>
    1272. 

  1272.         <b class="header">0.4.0</b><br />
    1273. 

  1273.         All Underscore functions can now be called in an object-oriented style,
    1274. 

  1274.         like so: <tt>_([1, 2, 3]).map(...);</tt>. Original patch provided by
    1275. 

  1275.         <a href="http://macournoyer.com/">Marc-André Cournoyer</a>.
    1276. 

  1276.         Wrapped objects can be chained through multiple
    1277. 

  1277.         method invocations. A <a href="#functions"><tt>functions</tt></a> method
    1278. 

  1278.         was added, providing a sorted list of all the functions in Underscore.
    1279. 

  1279.       </p>
    1280. 

  1280. 

  1281.       <p>
    1282. 

  1282.         <b class="header">0.3.3</b><br />
    1283. 

  1283.         Added the JavaScript 1.8 function <tt>reduceRight</tt>. Aliased it
    1284. 

  1284.         as <tt>foldr</tt>, and aliased <tt>reduce</tt> as <tt>foldl</tt>.
    1285. 

  1285.       </p>
    1286. 

  1286. 

  1287.       <p>
    1288. 

  1288.         <b class="header">0.3.2</b><br />
    1289. 

  1289.         Now runs on stock <a href="http://www.mozilla.org/rhino/">Rhino</a>
    1290. 

  1290.         interpreters with: <tt>load("underscore.js")</tt>.
    1291. 

  1291.         Added <a href="#identity"><tt>identity</tt></a> as a utility function.
    1292. 

  1292.       </p>
    1293. 

  1293. 

  1294.       <p>
    1295. 

  1295.         <b class="header">0.3.1</b><br />
    1296. 

  1296.         All iterators are now passed in the original collection as their third
    1297. 

  1297.         argument, the same as JavaScript 1.6's <b>forEach</b>. Iterating over
    1298. 

  1298.         objects is now called with <tt>(value, key, collection)</tt>, for details
    1299. 

  1299.         see <a href="#each"><tt>_.each</tt></a>.
    1300. 

  1300.       </p>
    1301. 

  1301. 

  1302.       <p>
    1303. 

  1303.         <b class="header">0.3.0</b><br />
    1304. 

  1304.         Added <a href="http://github.com/dmitryBaranovskiy">Dmitry Baranovskiy</a>'s
    1305. 

  1305.         comprehensive optimizations, merged in
    1306. 

  1306.         <a href="http://github.com/kriskowal/">Kris Kowal</a>'s patches to make Underscore
    1307. 

  1307.         <a href="http://wiki.commonjs.org/wiki/CommonJS">CommonJS</a> and
    1308. 

  1308.         <a href="http://narwhaljs.org/">Narwhal</a> compliant.
    1309. 

  1309.       </p>
    1310. 

  1310. 

  1311.       <p>
    1312. 

  1312.         <b class="header">0.2.0</b><br />
    1313. 

  1313.         Added <tt>compose</tt> and <tt>lastIndexOf</tt>, renamed <tt>inject</tt> to
    1314. 

  1314.         <tt>reduce</tt>, added aliases for <tt>inject</tt>, <tt>filter</tt>,
    1315. 

  1315.         <tt>every</tt>, <tt>some</tt>, and <tt>forEach</tt>.
    1316. 

  1316.       </p>
    1317. 

  1317. 

  1318.       <p>
    1319. 

  1319.         <b class="header">0.1.1</b><br />
    1320. 

  1320.         Added <tt>noConflict</tt>, so that the "Underscore" object can be assigned to
    1321. 

  1321.         other variables.
    1322. 

  1322.       </p>
    1323. 

  1323. 

  1324.       <p>
    1325. 

  1325.         <b class="header">0.1.0</b><br />
    1326. 

  1326.         Initial release of Underscore.js.
    1327. 

  1327.       </p>
    1328. 

  1328. 

  1329.       <p>
    1330. 

  1330.         <a href="http://documentcloud.org/" title="A DocumentCloud Project" style="background:none;">
    1331. 

  1331.           <img src="http://jashkenas.s3.amazonaws.com/images/a_documentcloud_project.png" alt="A DocumentCloud Project" />
    1332. 

  1332.         </a>
    1333. 

  1333.       </p>
    1334. 

  1334. 

  1335.     </div>
    1336. 

  1336. 

  1337.   </div>
    1338. 

  1338. 

  1339.   <!-- Include Underscore, so you can play with it in the console. -->
    1340. 

  1340.   <script type="text/javascript" src="underscore.js"></script>
    1341. 

  1341. 

  1342. </body>
    1343. 

  1343. </html>
    1344. 

  1344.