/ajax/libs//0.6.1/lodash.js
JavaScript | 1504 lines | 666 code | 126 blank | 712 comment | 221 complexity | 1f10ab2149d3be372539f5e775013893 MD5 | raw file
- /*!
- * Lo-Dash v0.6.1 <http://lodash.com>
- * Copyright 2012 John-David Dalton <http://allyoucanleet.com/>
- * Based on Underscore.js 1.3.3, copyright 2009-2012 Jeremy Ashkenas, DocumentCloud Inc.
- * <http://documentcloud.github.com/underscore>
- * Available under MIT license <http://lodash.com/license>
- */
- ;(function(window, undefined) {
- 'use strict';
- /**
- * Used to cache the last `_.templateSettings.evaluate` delimiter to avoid
- * unnecessarily assigning `reEvaluateDelimiter` a new generated regexp.
- * Assigned in `_.template`.
- */
- var lastEvaluateDelimiter;
- /**
- * Used to cache the last template `options.variable` to avoid unnecessarily
- * assigning `reDoubleVariable` a new generated regexp. Assigned in `_.template`.
- */
- var lastVariable;
- /**
- * Used to match potentially incorrect data object references, like `obj.obj`,
- * in compiled templates. Assigned in `_.template`.
- */
- var reDoubleVariable;
- /**
- * Used to match "evaluate" delimiters, including internal delimiters,
- * in template text. Assigned in `_.template`.
- */
- var reEvaluateDelimiter;
- /** Detect free variable `exports` */
- var freeExports = typeof exports == 'object' && exports &&
- (typeof global == 'object' && global && global == global.global && (window = global), exports);
- /** Native prototype shortcuts */
- var ArrayProto = Array.prototype,
- BoolProto = Boolean.prototype,
- ObjectProto = Object.prototype,
- NumberProto = Number.prototype,
- StringProto = String.prototype;
- /** Used to generate unique IDs */
- var idCounter = 0;
- /** Used by `cachedContains` as the default size when optimizations are enabled for large arrays */
- var largeArraySize = 30;
- /** Used to restore the original `_` reference in `noConflict` */
- var oldDash = window._;
- /** Used to detect delimiter values that should be processed by `tokenizeEvaluate` */
- var reComplexDelimiter = /[-+=!~*%&^<>|{(\/]|\[\D|\b(?:delete|in|instanceof|new|typeof|void)\b/;
- /** Used to match HTML entities */
- var reEscapedHtml = /&(?:amp|lt|gt|quot|#x27);/g;
- /** Used to match empty string literals in compiled template source */
- var reEmptyStringLeading = /\b__p \+= '';/g,
- reEmptyStringMiddle = /\b(__p \+=) '' \+/g,
- reEmptyStringTrailing = /(__e\(.*?\)|\b__t\)) \+\n'';/g;
- /** Used to match regexp flags from their coerced string values */
- var reFlags = /\w*$/;
- /** Used to insert the data object variable into compiled template source */
- var reInsertVariable = /(?:__e|__t = )\(\s*(?![\d\s"']|this\.)/g;
- /** Used to detect if a method is native */
- var reNative = RegExp('^' +
- (ObjectProto.valueOf + '')
- .replace(/[.*+?^=!:${}()|[\]\/\\]/g, '\\$&')
- .replace(/valueOf|for [^\]]+/g, '.+?') + '$'
- );
- /** Used to match internally used tokens in template text */
- var reToken = /__token__(\d+)/g;
- /** Used to match HTML characters */
- var reUnescapedHtml = /[&<>"']/g;
- /** Used to match unescaped characters in compiled string literals */
- var reUnescapedString = /['\n\r\t\u2028\u2029\\]/g;
- /** Used to fix the JScript [[DontEnum]] bug */
- var shadowed = [
- 'constructor', 'hasOwnProperty', 'isPrototypeOf', 'propertyIsEnumerable',
- 'toLocaleString', 'toString', 'valueOf'
- ];
- /** Used to make template sourceURLs easier to identify */
- var templateCounter = 0;
- /** Used to replace template delimiters */
- var token = '__token__';
- /** Used to store tokenized template text snippets */
- var tokenized = [];
- /** Native method shortcuts */
- var concat = ArrayProto.concat,
- hasOwnProperty = ObjectProto.hasOwnProperty,
- push = ArrayProto.push,
- propertyIsEnumerable = ObjectProto.propertyIsEnumerable,
- slice = ArrayProto.slice,
- toString = ObjectProto.toString;
- /* Native method shortcuts for methods with the same name as other `lodash` methods */
- var nativeBind = reNative.test(nativeBind = slice.bind) && nativeBind,
- nativeIsArray = reNative.test(nativeIsArray = Array.isArray) && nativeIsArray,
- nativeIsFinite = window.isFinite,
- nativeKeys = reNative.test(nativeKeys = Object.keys) && nativeKeys;
- /** `Object#toString` result shortcuts */
- var argsClass = '[object Arguments]',
- arrayClass = '[object Array]',
- boolClass = '[object Boolean]',
- dateClass = '[object Date]',
- funcClass = '[object Function]',
- numberClass = '[object Number]',
- objectClass = '[object Object]',
- regexpClass = '[object RegExp]',
- stringClass = '[object String]';
- /** Timer shortcuts */
- var clearTimeout = window.clearTimeout,
- setTimeout = window.setTimeout;
- /**
- * Detect the JScript [[DontEnum]] bug:
- *
- * In IE < 9 an objects own properties, shadowing non-enumerable ones, are
- * made non-enumerable as well.
- */
- var hasDontEnumBug;
- /**
- * Detect if `Array#shift` and `Array#splice` augment array-like objects
- * incorrectly:
- *
- * Firefox < 10, IE compatibility mode, and IE < 9 have buggy Array `shift()`
- * and `splice()` functions that fail to remove the last element, `value[0]`,
- * of array-like objects even though the `length` property is set to `0`.
- * The `shift()` method is buggy in IE 8 compatibility mode, while `splice()`
- * is buggy regardless of mode in IE < 9 and buggy in compatibility mode in IE 9.
- */
- var hasObjectSpliceBug;
- /** Detect if own properties are iterated after inherited properties (IE < 9) */
- var iteratesOwnLast;
- /** Detect if an `arguments` object's indexes are non-enumerable (IE < 9) */
- var noArgsEnum = true;
- (function() {
- var object = { '0': 1, 'length': 1 },
- props = [];
- function ctor() { this.x = 1; }
- ctor.prototype = { 'valueOf': 1, 'y': 1 };
- for (var prop in new ctor) { props.push(prop); }
- for (prop in arguments) { noArgsEnum = !prop; }
- hasDontEnumBug = (props + '').length < 4;
- iteratesOwnLast = props[0] != 'x';
- hasObjectSpliceBug = (props.splice.call(object, 0, 1), object[0]);
- }(1));
- /** Detect if an `arguments` object's [[Class]] is unresolvable (Firefox < 4, IE < 9) */
- var noArgsClass = !isArguments(arguments);
- /** Detect if `Array#slice` cannot be used to convert strings to arrays (Opera < 10.52) */
- var noArraySliceOnStrings = slice.call('x')[0] != 'x';
- /**
- * Detect lack of support for accessing string characters by index:
- *
- * IE < 8 can't access characters by index and IE 8 can only access
- * characters by index on string literals.
- */
- var noCharByIndex = ('x'[0] + Object('x')[0]) != 'xx';
- /**
- * Detect if a node's [[Class]] is unresolvable (IE < 9)
- * and that the JS engine won't error when attempting to coerce an object to
- * a string without a `toString` property value of `typeof` "function".
- */
- try {
- var noNodeClass = ({ 'toString': 0 } + '', toString.call(window.document || 0) == objectClass);
- } catch(e) { }
- /* Detect if `Function#bind` exists and is inferred to be fast (all but V8) */
- var isBindFast = nativeBind && /\n|Opera/.test(nativeBind + toString.call(window.opera));
- /* Detect if `Object.keys` exists and is inferred to be fast (IE, Opera, V8) */
- var isKeysFast = nativeKeys && /^.+$|true/.test(nativeKeys + !!window.attachEvent);
- /* Detect if strict mode, "use strict", is inferred to be fast (V8) */
- var isStrictFast = !isBindFast;
- /**
- * Detect if sourceURL syntax is usable without erroring:
- *
- * The JS engine in Adobe products, like InDesign, will throw a syntax error
- * when it encounters a single line comment beginning with the `@` symbol.
- *
- * The JS engine in Narwhal will generate the function `function anonymous(){//}`
- * and throw a syntax error.
- *
- * Avoid comments beginning `@` symbols in IE because they are part of its
- * non-standard conditional compilation support.
- * http://msdn.microsoft.com/en-us/library/121hztk3(v=vs.94).aspx
- */
- try {
- var useSourceURL = (Function('//@')(), !window.attachEvent);
- } catch(e){ }
- /** Used to identify object classifications that are array-like */
- var arrayLikeClasses = {};
- arrayLikeClasses[boolClass] = arrayLikeClasses[dateClass] = arrayLikeClasses[funcClass] =
- arrayLikeClasses[numberClass] = arrayLikeClasses[objectClass] = arrayLikeClasses[regexpClass] = false;
- arrayLikeClasses[argsClass] = arrayLikeClasses[arrayClass] = arrayLikeClasses[stringClass] = true;
- /** Used to identify object classifications that `_.clone` supports */
- var cloneableClasses = {};
- cloneableClasses[argsClass] = cloneableClasses[funcClass] = false;
- cloneableClasses[arrayClass] = cloneableClasses[boolClass] = cloneableClasses[dateClass] =
- cloneableClasses[numberClass] = cloneableClasses[objectClass] = cloneableClasses[regexpClass] =
- cloneableClasses[stringClass] = true;
- /**
- * Used to convert characters to HTML entities:
- *
- * Though the `>` character is escaped for symmetry, characters like `>` and `/`
- * don't require escaping in HTML and have no special meaning unless they're part
- * of a tag or an unquoted attribute value.
- * http://mathiasbynens.be/notes/ambiguous-ampersands (under "semi-related fun fact")
- */
- var htmlEscapes = {
- '&': '&',
- '<': '<',
- '>': '>',
- '"': '"',
- "'": '''
- };
- /** Used to convert HTML entities to characters */
- var htmlUnescapes = {
- '&': '&',
- '<': '<',
- '>': '>',
- '"': '"',
- ''': "'"
- };
- /** Used to determine if values are of the language type Object */
- var objectTypes = {
- 'boolean': false,
- 'function': true,
- 'object': true,
- 'number': false,
- 'string': false,
- 'undefined': false,
- 'unknown': true
- };
- /** Used to escape characters for inclusion in compiled string literals */
- var stringEscapes = {
- '\\': '\\',
- "'": "'",
- '\n': 'n',
- '\r': 'r',
- '\t': 't',
- '\u2028': 'u2028',
- '\u2029': 'u2029'
- };
- /*--------------------------------------------------------------------------*/
- /**
- * The `lodash` function.
- *
- * @name _
- * @constructor
- * @param {Mixed} value The value to wrap in a `LoDash` instance.
- * @returns {Object} Returns a `LoDash` instance.
- */
- function lodash(value) {
- // allow invoking `lodash` without the `new` operator
- return new LoDash(value);
- }
- /**
- * Creates a `LoDash` instance that wraps a value to allow chaining.
- *
- * @private
- * @constructor
- * @param {Mixed} value The value to wrap.
- */
- function LoDash(value) {
- // exit early if already wrapped
- if (value && value._wrapped) {
- return value;
- }
- this._wrapped = value;
- }
- /**
- * By default, the template delimiters used by Lo-Dash are similar to those in
- * embedded Ruby (ERB). Change the following template settings to use alternative
- * delimiters.
- *
- * @static
- * @memberOf _
- * @type Object
- */
- lodash.templateSettings = {
- /**
- * Used to detect `data` property values to be HTML-escaped.
- *
- * @static
- * @memberOf _.templateSettings
- * @type RegExp
- */
- 'escape': /<%-([\s\S]+?)%>/g,
- /**
- * Used to detect code to be evaluated.
- *
- * @static
- * @memberOf _.templateSettings
- * @type RegExp
- */
- 'evaluate': /<%([\s\S]+?)%>/g,
- /**
- * Used to detect `data` property values to inject.
- *
- * @static
- * @memberOf _.templateSettings
- * @type RegExp
- */
- 'interpolate': /<%=([\s\S]+?)%>/g,
- /**
- * Used to reference the data object in the template text.
- *
- * @static
- * @memberOf _.templateSettings
- * @type String
- */
- 'variable': ''
- };
- /*--------------------------------------------------------------------------*/
- /**
- * The template used to create iterator functions.
- *
- * @private
- * @param {Obect} data The data object used to populate the text.
- * @returns {String} Returns the interpolated text.
- */
- var iteratorTemplate = template(
- // conditional strict mode
- '<% if (useStrict) { %>\'use strict\';\n<% } %>' +
- // the `iteratee` may be reassigned by the `top` snippet
- 'var index, value, iteratee = <%= firstArg %>, ' +
- // assign the `result` variable an initial value
- 'result<% if (init) { %> = <%= init %><% } %>;\n' +
- // add code to exit early or do so if the first argument is falsey
- '<%= exit %>;\n' +
- // add code after the exit snippet but before the iteration branches
- '<%= top %>;\n' +
- // the following branch is for iterating arrays and array-like objects
- '<% if (arrayBranch) { %>' +
- 'var length = iteratee.length; index = -1;' +
- ' <% if (objectBranch) { %>\nif (length > -1 && length === length >>> 0) {<% } %>' +
- // add support for accessing string characters by index if needed
- ' <% if (noCharByIndex) { %>\n' +
- ' if (toString.call(iteratee) == stringClass) {\n' +
- ' iteratee = iteratee.split(\'\')\n' +
- ' }' +
- ' <% } %>\n' +
- ' <%= arrayBranch.beforeLoop %>;\n' +
- ' while (++index < length) {\n' +
- ' value = iteratee[index];\n' +
- ' <%= arrayBranch.inLoop %>\n' +
- ' }' +
- ' <% if (objectBranch) { %>\n}<% } %>' +
- '<% } %>' +
- // the following branch is for iterating an object's own/inherited properties
- '<% if (objectBranch) { %>' +
- ' <% if (arrayBranch) { %>\nelse {' +
- // add support for iterating over `arguments` objects if needed
- ' <% } else if (noArgsEnum) { %>\n' +
- ' var length = iteratee.length; index = -1;\n' +
- ' if (length && isArguments(iteratee)) {\n' +
- ' while (++index < length) {\n' +
- ' value = iteratee[index += \'\'];\n' +
- ' <%= objectBranch.inLoop %>\n' +
- ' }\n' +
- ' } else {' +
- ' <% } %>' +
- // Firefox < 3.6, Opera > 9.50 - Opera < 11.60, and Safari < 5.1
- // (if the prototype or a property on the prototype has been set)
- // incorrectly sets a function's `prototype` property [[Enumerable]]
- // value to `true`. Because of this Lo-Dash standardizes on skipping
- // the the `prototype` property of functions regardless of its
- // [[Enumerable]] value.
- ' <% if (!hasDontEnumBug) { %>\n' +
- ' var skipProto = typeof iteratee == \'function\' && \n' +
- ' propertyIsEnumerable.call(iteratee, \'prototype\');\n' +
- ' <% } %>' +
- // iterate own properties using `Object.keys` if it's fast
- ' <% if (isKeysFast && useHas) { %>\n' +
- ' var ownIndex = -1,\n' +
- ' ownProps = objectTypes[typeof iteratee] ? nativeKeys(iteratee) : [],\n' +
- ' length = ownProps.length;\n\n' +
- ' <%= objectBranch.beforeLoop %>;\n' +
- ' while (++ownIndex < length) {\n' +
- ' index = ownProps[ownIndex];\n' +
- ' <% if (!hasDontEnumBug) { %>if (!(skipProto && index == \'prototype\')) {\n <% } %>' +
- ' value = iteratee[index];\n' +
- ' <%= objectBranch.inLoop %>\n' +
- ' <% if (!hasDontEnumBug) { %>}\n<% } %>' +
- ' }' +
- // else using a for-in loop
- ' <% } else { %>\n' +
- ' <%= objectBranch.beforeLoop %>;\n' +
- ' for (index in iteratee) {' +
- ' <% if (!hasDontEnumBug || useHas) { %>\n if (<%' +
- ' if (!hasDontEnumBug) { %>!(skipProto && index == \'prototype\')<% }' +
- ' if (!hasDontEnumBug && useHas) { %> && <% }' +
- ' if (useHas) { %>hasOwnProperty.call(iteratee, index)<% }' +
- ' %>) {' +
- ' <% } %>\n' +
- ' value = iteratee[index];\n' +
- ' <%= objectBranch.inLoop %>;\n' +
- ' <% if (!hasDontEnumBug || useHas) { %>}\n<% } %>' +
- ' }' +
- ' <% } %>' +
- // Because IE < 9 can't set the `[[Enumerable]]` attribute of an
- // existing property and the `constructor` property of a prototype
- // defaults to non-enumerable, Lo-Dash skips the `constructor`
- // property when it infers it's iterating over a `prototype` object.
- ' <% if (hasDontEnumBug) { %>\n\n' +
- ' var ctor = iteratee.constructor;\n' +
- ' <% for (var k = 0; k < 7; k++) { %>\n' +
- ' index = \'<%= shadowed[k] %>\';\n' +
- ' if (<%' +
- ' if (shadowed[k] == \'constructor\') {' +
- ' %>!(ctor && ctor.prototype === iteratee) && <%' +
- ' } %>hasOwnProperty.call(iteratee, index)) {\n' +
- ' value = iteratee[index];\n' +
- ' <%= objectBranch.inLoop %>\n' +
- ' }' +
- ' <% } %>' +
- ' <% } %>' +
- ' <% if (arrayBranch || noArgsEnum) { %>\n}<% } %>' +
- '<% } %>\n' +
- // add code to the bottom of the iteration function
- '<%= bottom %>;\n' +
- // finally, return the `result`
- 'return result'
- );
- /**
- * Reusable iterator options shared by
- * `every`, `filter`, `find`, `forEach`, `forIn`, `forOwn`, `groupBy`, `map`,
- * `reject`, `some`, and `sortBy`.
- */
- var baseIteratorOptions = {
- 'args': 'collection, callback, thisArg',
- 'init': 'collection',
- 'top':
- 'if (!callback) {\n' +
- ' callback = identity\n' +
- '}\n' +
- 'else if (thisArg) {\n' +
- ' callback = iteratorBind(callback, thisArg)\n' +
- '}',
- 'inLoop': 'if (callback(value, index, collection) === false) return result'
- };
- /** Reusable iterator options for `countBy`, `groupBy`, and `sortBy` */
- var countByIteratorOptions = {
- 'init': '{}',
- 'top':
- 'var prop;\n' +
- 'if (typeof callback != \'function\') {\n' +
- ' var valueProp = callback;\n' +
- ' callback = function(value) { return value[valueProp] }\n' +
- '}\n' +
- 'else if (thisArg) {\n' +
- ' callback = iteratorBind(callback, thisArg)\n' +
- '}',
- 'inLoop':
- 'prop = callback(value, index, collection);\n' +
- '(hasOwnProperty.call(result, prop) ? result[prop]++ : result[prop] = 1)'
- };
- /** Reusable iterator options for `drop` and `pick` */
- var dropIteratorOptions = {
- 'useHas': false,
- 'args': 'object, callback, thisArg',
- 'init': '{}',
- 'top':
- 'var isFunc = typeof callback == \'function\';\n' +
- 'if (!isFunc) {\n' +
- ' var props = concat.apply(ArrayProto, arguments)\n' +
- '} else if (thisArg) {\n' +
- ' callback = iteratorBind(callback, thisArg)\n' +
- '}',
- 'inLoop':
- 'if (isFunc\n' +
- ' ? !callback(value, index, object)\n' +
- ' : indexOf(props, index) < 0\n' +
- ') result[index] = value'
- };
- /** Reusable iterator options for `every` and `some` */
- var everyIteratorOptions = {
- 'init': 'true',
- 'inLoop': 'if (!callback(value, index, collection)) return !result'
- };
- /** Reusable iterator options for `defaults` and `extend` */
- var extendIteratorOptions = {
- 'useHas': false,
- 'useStrict': false,
- 'args': 'object',
- 'init': 'object',
- 'top':
- 'for (var argsIndex = 1, argsLength = arguments.length; argsIndex < argsLength; argsIndex++) {\n' +
- ' if (iteratee = arguments[argsIndex]) {',
- 'inLoop': 'result[index] = value',
- 'bottom': ' }\n}'
- };
- /** Reusable iterator options for `filter`, `reject`, and `where` */
- var filterIteratorOptions = {
- 'init': '[]',
- 'inLoop': 'callback(value, index, collection) && result.push(value)'
- };
- /** Reusable iterator options for `find`, `forEach`, `forIn`, and `forOwn` */
- var forEachIteratorOptions = {
- 'top': 'if (thisArg) callback = iteratorBind(callback, thisArg)'
- };
- /** Reusable iterator options for `forIn` and `forOwn` */
- var forOwnIteratorOptions = {
- 'inLoop': {
- 'object': baseIteratorOptions.inLoop
- }
- };
- /** Reusable iterator options for `invoke`, `map`, `pluck`, and `sortBy` */
- var mapIteratorOptions = {
- 'init': '',
- 'exit': 'if (!collection) return []',
- 'beforeLoop': {
- 'array': 'result = Array(length)',
- 'object': 'result = ' + (isKeysFast ? 'Array(length)' : '[]')
- },
- 'inLoop': {
- 'array': 'result[index] = callback(value, index, collection)',
- 'object': 'result' + (isKeysFast ? '[ownIndex] = ' : '.push') + '(callback(value, index, collection))'
- }
- };
- /*--------------------------------------------------------------------------*/
- /**
- * Creates a new function optimized for searching large arrays for a given `value`,
- * starting at `fromIndex`, using strict equality for comparisons, i.e. `===`.
- *
- * @private
- * @param {Array} array The array to search.
- * @param {Mixed} value The value to search for.
- * @param {Number} [fromIndex=0] The index to start searching from.
- * @param {Number} [largeSize=30] The length at which an array is considered large.
- * @returns {Boolean} Returns `true` if `value` is found, else `false`.
- */
- function cachedContains(array, fromIndex, largeSize) {
- fromIndex || (fromIndex = 0);
- var length = array.length,
- isLarge = (length - fromIndex) >= (largeSize || largeArraySize),
- cache = isLarge ? {} : array;
- if (isLarge) {
- // init value cache
- var key,
- index = fromIndex - 1;
- while (++index < length) {
- // manually coerce `value` to string because `hasOwnProperty`, in some
- // older versions of Firefox, coerces objects incorrectly
- key = array[index] + '';
- (hasOwnProperty.call(cache, key) ? cache[key] : (cache[key] = [])).push(array[index]);
- }
- }
- return function(value) {
- if (isLarge) {
- var key = value + '';
- return hasOwnProperty.call(cache, key) && indexOf(cache[key], value) > -1;
- }
- return indexOf(cache, value, fromIndex) > -1;
- }
- }
- /**
- * Creates compiled iteration functions. The iteration function will be created
- * to iterate over only objects if the first argument of `options.args` is
- * "object" or `options.inLoop.array` is falsey.
- *
- * @private
- * @param {Object} [options1, options2, ...] The compile options objects.
- *
- * useHas - A boolean to specify whether or not to use `hasOwnProperty` checks
- * in the object loop.
- *
- * useStrict - A boolean to specify whether or not to include the ES5
- * "use strict" directive.
- *
- * args - A string of comma separated arguments the iteration function will
- * accept.
- *
- * init - A string to specify the initial value of the `result` variable.
- *
- * exit - A string of code to use in place of the default exit-early check
- * of `if (!arguments[0]) return result`.
- *
- * top - A string of code to execute after the exit-early check but before
- * the iteration branches.
- *
- * beforeLoop - A string or object containing an "array" or "object" property
- * of code to execute before the array or object loops.
- *
- * inLoop - A string or object containing an "array" or "object" property
- * of code to execute in the array or object loops.
- *
- * bottom - A string of code to execute after the iteration branches but
- * before the `result` is returned.
- *
- * @returns {Function} Returns the compiled function.
- */
- function createIterator() {
- var object,
- prop,
- value,
- index = -1,
- length = arguments.length;
- // merge options into a template data object
- var data = {
- 'bottom': '',
- 'exit': '',
- 'init': '',
- 'top': '',
- 'arrayBranch': { 'beforeLoop': '' },
- 'objectBranch': { 'beforeLoop': '' }
- };
- while (++index < length) {
- object = arguments[index];
- for (prop in object) {
- value = (value = object[prop]) == null ? '' : value;
- // keep this regexp explicit for the build pre-process
- if (/beforeLoop|inLoop/.test(prop)) {
- if (typeof value == 'string') {
- value = { 'array': value, 'object': value };
- }
- data.arrayBranch[prop] = value.array || '';
- data.objectBranch[prop] = value.object || '';
- } else {
- data[prop] = value;
- }
- }
- }
- // set additional template `data` values
- var args = data.args,
- firstArg = /^[^,]+/.exec(args)[0],
- useStrict = data.useStrict;
- data.firstArg = firstArg;
- data.hasDontEnumBug = hasDontEnumBug;
- data.isKeysFast = isKeysFast;
- data.noArgsEnum = noArgsEnum;
- data.shadowed = shadowed;
- data.useHas = data.useHas !== false;
- data.useStrict = useStrict == null ? isStrictFast : useStrict;
- if (data.noCharByIndex == null) {
- data.noCharByIndex = noCharByIndex;
- }
- if (!data.exit) {
- data.exit = 'if (!' + firstArg + ') return result';
- }
- if (firstArg != 'collection' || !data.arrayBranch.inLoop) {
- data.arrayBranch = null;
- }
- // create the function factory
- var factory = Function(
- 'arrayLikeClasses, ArrayProto, bind, compareAscending, concat, forIn, ' +
- 'hasOwnProperty, identity, indexOf, isArguments, isArray, isFunction, ' +
- 'isPlainObject, iteratorBind, objectClass, objectTypes, nativeKeys, ' +
- 'propertyIsEnumerable, slice, stringClass, toString',
- 'var callee = function(' + args + ') {\n' + iteratorTemplate(data) + '\n};\n' +
- 'return callee'
- );
- // return the compiled function
- return factory(
- arrayLikeClasses, ArrayProto, bind, compareAscending, concat, forIn,
- hasOwnProperty, identity, indexOf, isArguments, isArray, isFunction,
- isPlainObject, iteratorBind, objectClass, objectTypes, nativeKeys,
- propertyIsEnumerable, slice, stringClass, toString
- );
- }
- /**
- * Used by `sortBy` to compare transformed `collection` values, stable sorting
- * them in ascending order.
- *
- * @private
- * @param {Object} a The object to compare to `b`.
- * @param {Object} b The object to compare to `a`.
- * @returns {Number} Returns the sort order indicator of `1` or `-1`.
- */
- function compareAscending(a, b) {
- var ai = a.index,
- bi = b.index;
- a = a.criteria;
- b = b.criteria;
- if (a === undefined) {
- return 1;
- }
- if (b === undefined) {
- return -1;
- }
- // ensure a stable sort in V8 and other engines
- // http://code.google.com/p/v8/issues/detail?id=90
- return a < b ? -1 : a > b ? 1 : ai < bi ? -1 : 1;
- }
- /**
- * Used by `template` to replace tokens with their corresponding code snippets.
- *
- * @private
- * @param {String} match The matched token.
- * @param {String} index The `tokenized` index of the code snippet.
- * @returns {String} Returns the code snippet.
- */
- function detokenize(match, index) {
- return tokenized[index];
- }
- /**
- * Used by `template` to escape characters for inclusion in compiled
- * string literals.
- *
- * @private
- * @param {String} match The matched character to escape.
- * @returns {String} Returns the escaped character.
- */
- function escapeStringChar(match) {
- return '\\' + stringEscapes[match];
- }
- /**
- * Used by `escape` to convert characters to HTML entities.
- *
- * @private
- * @param {String} match The matched character to escape.
- * @returns {String} Returns the escaped character.
- */
- function escapeHtmlChar(match) {
- return htmlEscapes[match];
- }
- /**
- * Creates a new function that, when called, invokes `func` with the `this`
- * binding of `thisArg` and the arguments (value, index, object).
- *
- * @private
- * @param {Function} func The function to bind.
- * @param {Mixed} [thisArg] The `this` binding of `func`.
- * @returns {Function} Returns the new bound function.
- */
- function iteratorBind(func, thisArg) {
- return function(value, index, object) {
- return func.call(thisArg, value, index, object);
- };
- }
- /**
- * A no-operation function.
- *
- * @private
- */
- function noop() {
- // no operation performed
- }
- /**
- * Used by `template` to replace "escape" template delimiters with tokens.
- *
- * @private
- * @param {String} match The matched template delimiter.
- * @param {String} value The delimiter value.
- * @returns {String} Returns a token.
- */
- function tokenizeEscape(match, value) {
- if (match && reComplexDelimiter.test(value)) {
- return '<e%-' + value + '%>';
- }
- var index = tokenized.length;
- tokenized[index] = "' +\n__e(" + value + ") +\n'";
- return token + index;
- }
- /**
- * Used by `template` to replace "evaluate" template delimiters, or complex
- * "escape" and "interpolate" delimiters, with tokens.
- *
- * @private
- * @param {String} match The matched template delimiter.
- * @param {String} escapeValue The complex "escape" delimiter value.
- * @param {String} interpolateValue The complex "interpolate" delimiter value.
- * @param {String} [evaluateValue] The "evaluate" delimiter value.
- * @returns {String} Returns a token.
- */
- function tokenizeEvaluate(match, escapeValue, interpolateValue, evaluateValue) {
- if (evaluateValue) {
- var index = tokenized.length;
- tokenized[index] = "';\n" + evaluateValue + ";\n__p += '";
- return token + index;
- }
- return escapeValue
- ? tokenizeEscape(null, escapeValue)
- : tokenizeInterpolate(null, interpolateValue);
- }
- /**
- * Used by `template` to replace "interpolate" template delimiters with tokens.
- *
- * @private
- * @param {String} match The matched template delimiter.
- * @param {String} value The delimiter value.
- * @returns {String} Returns a token.
- */
- function tokenizeInterpolate(match, value) {
- if (match && reComplexDelimiter.test(value)) {
- return '<e%=' + value + '%>';
- }
- var index = tokenized.length;
- tokenized[index] = "' +\n((__t = (" + value + ")) == null ? '' : __t) +\n'";
- return token + index;
- }
- /**
- * Used by `unescape` to convert HTML entities to characters.
- *
- * @private
- * @param {String} match The matched character to unescape.
- * @returns {String} Returns the unescaped character.
- */
- function unescapeHtmlChar(match) {
- return htmlUnescapes[match];
- }
- /*--------------------------------------------------------------------------*/
- /**
- * Checks if `value` is an `arguments` object.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to check.
- * @returns {Boolean} Returns `true` if the `value` is an `arguments` object, else `false`.
- * @example
- *
- * (function() { return _.isArguments(arguments); })(1, 2, 3);
- * // => true
- *
- * _.isArguments([1, 2, 3]);
- * // => false
- */
- function isArguments(value) {
- return toString.call(value) == argsClass;
- }
- // fallback for browsers that can't detect `arguments` objects by [[Class]]
- if (noArgsClass) {
- isArguments = function(value) {
- return !!(value && hasOwnProperty.call(value, 'callee'));
- };
- }
- /**
- * Checks if `value` is an array.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to check.
- * @returns {Boolean} Returns `true` if the `value` is an array, else `false`.
- * @example
- *
- * (function() { return _.isArray(arguments); })();
- * // => false
- *
- * _.isArray([1, 2, 3]);
- * // => true
- */
- var isArray = nativeIsArray || function(value) {
- return toString.call(value) == arrayClass;
- };
- /**
- * Checks if `value` is a function.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to check.
- * @returns {Boolean} Returns `true` if the `value` is a function, else `false`.
- * @example
- *
- * _.isFunction(''.concat);
- * // => true
- */
- function isFunction(value) {
- return typeof value == 'function';
- }
- // fallback for older versions of Chrome and Safari
- if (isFunction(/x/)) {
- isFunction = function(value) {
- return toString.call(value) == funcClass;
- };
- }
- /**
- * Checks if a given `value` is an object created by the `Object` constructor
- * assuming objects created by the `Object` constructor have no inherited
- * enumerable properties and that there are no `Object.prototype` extensions.
- *
- * @private
- * @param {Mixed} value The value to check.
- * @param {Boolean} [skipArgsCheck=false] Internally used to skip checks for
- * `arguments` objects.
- * @returns {Boolean} Returns `true` if the `value` is a plain `Object` object,
- * else `false`.
- */
- function isPlainObject(value, skipArgsCheck) {
- return value
- ? value == ObjectProto || (value.__proto__ == ObjectProto && (skipArgsCheck || !isArguments(value)))
- : false;
- }
- // fallback for IE
- if (!isPlainObject(objectTypes)) {
- isPlainObject = function(value, skipArgsCheck) {
- // avoid non-objects and false positives for `arguments` objects
- var result = false;
- if (!(value && typeof value == 'object') || (!skipArgsCheck && isArguments(value))) {
- return result;
- }
- // IE < 9 presents DOM nodes as `Object` objects except they have `toString`
- // methods that are `typeof` "string" and still can coerce nodes to strings.
- // Also check that the constructor is `Object` (i.e. `Object instanceof Object`)
- var ctor = value.constructor;
- if ((!noNodeClass || !(typeof value.toString != 'function' && typeof (value + '') == 'string')) &&
- (!isFunction(ctor) || ctor instanceof ctor)) {
- // IE < 9 iterates inherited properties before own properties. If the first
- // iterated property is an object's own property then there are no inherited
- // enumerable properties.
- if (iteratesOwnLast) {
- forIn(value, function(objValue, objKey) {
- result = !hasOwnProperty.call(value, objKey);
- return false;
- });
- return result === false;
- }
- // In most environments an object's own properties are iterated before
- // its inherited properties. If the last iterated property is an object's
- // own property then there are no inherited enumerable properties.
- forIn(value, function(objValue, objKey) {
- result = objKey;
- });
- return result === false || hasOwnProperty.call(value, result);
- }
- return result;
- };
- }
- /**
- * A shim implementation of `Object.keys` that produces an array of the given
- * object's own enumerable property names.
- *
- * @private
- * @param {Object} object The object to inspect.
- * @returns {Array} Returns a new array of property names.
- */
- var shimKeys = createIterator({
- 'args': 'object',
- 'init': '[]',
- 'inLoop': 'result.push(index)'
- });
- /*--------------------------------------------------------------------------*/
- /**
- * Creates a clone of `value`. If `deep` is `true`, all nested objects will
- * also be cloned otherwise they will be assigned by reference. If a value has
- * a `clone` method it will be used to perform the clone. Functions, DOM nodes,
- * `arguments` objects, and objects created by constructors other than `Object`
- * are **not** cloned unless they have a custom `clone` method.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to clone.
- * @param {Boolean} deep A flag to indicate a deep clone.
- * @param {Object} [guard] Internally used to allow this method to work with
- * others like `_.map` without using their callback `index` argument for `deep`.
- * @param {Array} [stack=[]] Internally used to keep track of traversed objects
- * to avoid circular references.
- * @param {Object} thorough Internally used to indicate whether or not to perform
- * a more thorough clone of non-object values.
- * @returns {Mixed} Returns the cloned `value`.
- * @example
- *
- * var stooges = [
- * { 'name': 'moe', 'age': 40 },
- * { 'name': 'larry', 'age': 50 },
- * { 'name': 'curly', 'age': 60 }
- * ];
- *
- * _.clone({ 'name': 'moe' });
- * // => { 'name': 'moe' }
- *
- * var shallow = _.clone(stooges);
- * shallow[0] === stooges[0];
- * // => true
- *
- * var deep = _.clone(stooges, true);
- * shallow[0] === stooges[0];
- * // => false
- */
- function clone(value, deep, guard, stack, thorough) {
- if (value == null) {
- return value;
- }
- if (guard) {
- deep = false;
- }
- // avoid slower checks on primitives
- thorough || (thorough = { 'value': null });
- if (thorough.value == null) {
- // primitives passed from iframes use the primary document's native prototypes
- thorough.value = !!(BoolProto.clone || NumberProto.clone || StringProto.clone);
- }
- // use custom `clone` method if available
- var isObj = objectTypes[typeof value];
- if ((isObj || thorough.value) && value.clone && isFunction(value.clone)) {
- thorough.value = null;
- return value.clone(deep);
- }
- // inspect [[Class]]
- if (isObj) {
- // don't clone `arguments` objects, functions, or non-object Objects
- var className = toString.call(value);
- if (!cloneableClasses[className] || (noArgsClass && isArguments(value))) {
- return value;
- }
- var isArr = className == arrayClass;
- isObj = isArr || (className == objectClass ? isPlainObject(value, true) : isObj);
- }
- // shallow clone
- if (!isObj || !deep) {
- // don't clone functions
- return isObj
- ? (isArr ? slice.call(value) : extend({}, value))
- : value;
- }
- var ctor = value.constructor;
- switch (className) {
- case boolClass:
- return new ctor(value == true);
- case dateClass:
- return new ctor(+value);
- case numberClass:
- case stringClass:
- return new ctor(value);
- case regexpClass:
- return ctor(value.source, reFlags.exec(value));
- }
- // check for circular references and return corresponding clone
- stack || (stack = []);
- var length = stack.length;
- while (length--) {
- if (stack[length].source == value) {
- return stack[length].value;
- }
- }
- // init cloned object
- length = value.length;
- var result = isArr ? ctor(length) : {};
- // add current clone and original source value to the stack of traversed objects
- stack.push({ 'value': result, 'source': value });
- // recursively populate clone (susceptible to call stack limits)
- if (isArr) {
- var index = -1;
- while (++index < length) {
- result[index] = clone(value[index], deep, null, stack, thorough);
- }
- } else {
- forOwn(value, function(objValue, key) {
- result[key] = clone(objValue, deep, null, stack, thorough);
- });
- }
- return result;
- }
- /**
- * Assigns enumerable properties of the default object(s) to the `destination`
- * object for all `destination` properties that resolve to `null`/`undefined`.
- * Once a property is set, additional defaults of the same property will be
- * ignored.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Object} object The destination object.
- * @param {Object} [default1, default2, ...] The default objects.
- * @returns {Object} Returns the destination object.
- * @example
- *
- * var iceCream = { 'flavor': 'chocolate' };
- * _.defaults(iceCream, { 'flavor': 'vanilla', 'sprinkles': 'rainbow' });
- * // => { 'flavor': 'chocolate', 'sprinkles': 'rainbow' }
- */
- var defaults = createIterator(extendIteratorOptions, {
- 'inLoop': 'if (result[index] == null) ' + extendIteratorOptions.inLoop
- });
- /**
- * Creates a shallow clone of `object` excluding the specified properties.
- * Property names may be specified as individual arguments or as arrays of
- * property names. If `callback` is passed, it will be executed for each property
- * in the `object`, dropping the properties `callback` returns truthy for. The
- * `callback` is bound to `thisArg` and invoked with 3 arguments; (value, key, object).
- *
- * @static
- * @memberOf _
- * @alias omit
- * @category Objects
- * @param {Object} object The source object.
- * @param {Function|String} callback|[prop1, prop2, ...] The properties to drop
- * or the function called per iteration.
- * @param {Mixed} [thisArg] The `this` binding for the callback.
- * @returns {Object} Returns an object without the dropped properties.
- * @example
- *
- * _.drop({ 'name': 'moe', 'age': 40, 'userid': 'moe1' }, 'userid');
- * // => { 'name': 'moe', 'age': 40 }
- *
- * _.drop({ 'name': 'moe', '_hint': 'knucklehead', '_seed': '96c4eb' }, function(value, key) {
- * return key.charAt(0) == '_';
- * });
- * // => { 'name': 'moe' }
- */
- var drop = createIterator(dropIteratorOptions);
- /**
- * Assigns enumerable properties of the source object(s) to the `destination`
- * object. Subsequent sources will overwrite propery assignments of previous
- * sources.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Object} object The destination object.
- * @param {Object} [source1, source2, ...] The source objects.
- * @returns {Object} Returns the destination object.
- * @example
- *
- * _.extend({ 'name': 'moe' }, { 'age': 40 });
- * // => { 'name': 'moe', 'age': 40 }
- */
- var extend = createIterator(extendIteratorOptions);
- /**
- * Iterates over `object`'s own and inherited enumerable properties, executing
- * the `callback` for each property. The `callback` is bound to `thisArg` and
- * invoked with 3 arguments; (value, key, object). Callbacks may exit iteration
- * early by explicitly returning `false`.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Object} object The object to iterate over.
- * @param {Function} callback The function called per iteration.
- * @param {Mixed} [thisArg] The `this` binding for the callback.
- * @returns {Object} Returns `object`.
- * @example
- *
- * function Dog(name) {
- * this.name = name;
- * }
- *
- * Dog.prototype.bark = function() {
- * alert('Woof, woof!');
- * };
- *
- * _.forIn(new Dog('Dagny'), function(value, key) {
- * alert(key);
- * });
- * // => alerts 'name' and 'bark' (order is not guaranteed)
- */
- var forIn = createIterator(baseIteratorOptions, forEachIteratorOptions, forOwnIteratorOptions, {
- 'useHas': false
- });
- /**
- * Iterates over `object`'s own enumerable properties, executing the `callback`
- * for each property. The `callback` is bound to `thisArg` and invoked with 3
- * arguments; (value, key, object). Callbacks may exit iteration early by
- * explicitly returning `false`.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Object} object The object to iterate over.
- * @param {Function} callback The function called per iteration.
- * @param {Mixed} [thisArg] The `this` binding for the callback.
- * @returns {Object} Returns `object`.
- * @example
- *
- * _.forOwn({ '0': 'zero', '1': 'one', 'length': 2 }, function(num, key) {
- * alert(key);
- * });
- * // => alerts '0', '1', and 'length' (order is not guaranteed)
- */
- var forOwn = createIterator(baseIteratorOptions, forEachIteratorOptions, forOwnIteratorOptions);
- /**
- * Creates a sorted array of all enumerable properties, own and inherited,
- * of `object` that have function values.
- *
- * @static
- * @memberOf _
- * @alias methods
- * @category Objects
- * @param {Object} object The object to inspect.
- * @returns {Array} Returns a new array of property names that have function values.
- * @example
- *
- * _.functions(_);
- * // => ['all', 'any', 'bind', 'bindAll', 'clone', 'compact', 'compose', ...]
- */
- var functions = createIterator({
- 'useHas': false,
- 'args': 'object',
- 'init': '[]',
- 'inLoop': 'if (isFunction(value)) result.push(index)',
- 'bottom': 'result.sort()'
- });
- /**
- * Checks if the specified object `property` exists and is a direct property,
- * instead of an inherited property.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Object} object The object to check.
- * @param {String} property The property to check for.
- * @returns {Boolean} Returns `true` if key is a direct property, else `false`.
- * @example
- *
- * _.has({ 'a': 1, 'b': 2, 'c': 3 }, 'b');
- * // => true
- */
- function has(object, property) {
- return object ? hasOwnProperty.call(object, property) : false;
- }
- /**
- * Checks if `value` is a boolean (`true` or `false`) value.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to check.
- * @returns {Boolean} Returns `true` if the `value` is a boolean value, else `false`.
- * @example
- *
- * _.isBoolean(null);
- * // => false
- */
- function isBoolean(value) {
- return value === true || value === false || toString.call(value) == boolClass;
- }
- /**
- * Checks if `value` is a date.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to check.
- * @returns {Boolean} Returns `true` if the `value` is a date, else `false`.
- * @example
- *
- * _.isDate(new Date);
- * // => true
- */
- function isDate(value) {
- return toString.call(value) == dateClass;
- }
- /**
- * Checks if `value` is a DOM element.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} value The value to check.
- * @returns {Boolean} Returns `true` if the `value` is a DOM element, else `false`.
- * @example
- *
- * _.isElement(document.body);
- * // => true
- */
- function isElement(value) {
- return value ? value.nodeType === 1 : false;
- }
- /**
- * Checks if `value` is empty. Arrays, strings, or `arguments` objects with a
- * length of `0` and objects with no own enumerable properties are considered
- * "empty".
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Array|Object|String} value The value to inspect.
- * @returns {Boolean} Returns `true` if the `value` is empty, else `false`.
- * @example
- *
- * _.isEmpty([1, 2, 3]);
- * // => false
- *
- * _.isEmpty({});
- * // => true
- *
- * _.isEmpty('');
- * // => true
- */
- var isEmpty = createIterator({
- 'args': 'value',
- 'init': 'true',
- 'top':
- 'var className = toString.call(value),\n' +
- ' length = value.length;\n' +
- 'if (arrayLikeClasses[className]' +
- (noArgsClass ? ' || isArguments(value)' : '') + ' ||\n' +
- ' (className == objectClass && length > -1 && length === length >>> 0 &&\n' +
- ' isFunction(value.splice))' +
- ') return !length',
- 'inLoop': {
- 'object': 'return false'
- }
- });
- /**
- * Performs a deep comparison between two values to determine if they are
- * equivalent to each other. If a value has an `isEqual` method it will be
- * used to perform the comparison.
- *
- * @static
- * @memberOf _
- * @category Objects
- * @param {Mixed} a The value to compare.
- * @param {Mixed} b The other value to compare.
- * @param {Array} [stack=[]] Internally used to keep track of traversed objects
- * to avoid circular references.
- * @param {Object} thorough Internally used to indicate whether or not to perform
- * a more thorough comparison of non-object values.
- * @returns {Boolean} Returns `true` if the values are equvalent, else `false`.
- * @example
- *
- * var moe = { 'name': 'moe', 'luckyNumbers': [13, 27, 34] };
- * var clone = { 'name': 'moe', 'luckyNumbers': [13, 27, 34] };
- *
- * moe == clone;
- * // => false
- *
- * _.isEqual(moe, clone);
- * // => true
- */
- function isEqual(a, b, stack, thorough) {
- // a strict comparison is necessary because `null == undefined`
- if (a == null || b == null) {
- return a === b;
- }
- // avoid slower checks on non-objects
- thorough || (thorough = { 'value': null });
- if (thorough.value == null) {
- // primitives passed from iframes use the primary document's native prototypes
- thorough.value = !!(BoolProto.isEqual || NumberProto.isEqual || StringProto.isEqual);
- }
- if (objectTypes[typeof a] || objectTypes[typeof b] || thorough.value) {
- // unwrap any LoDash wrapped values
- if (a._chain) {
- a = a._wrapped;
- }
- if (b._chain) {
- b = b._wrapped;
- }
- // use custom `isEqual` method if available
- if (a.isEqual && isFunction(a.isEqual)) {
- thorough.value = null;
- return a.isEqual(b);
- }
- if (b.isEqual && isFunction(b.isEqual)) {
- thorough.value = null;
- return b.isEqual(a);
- }
- }
- // exit early for identical values
- if (a === b) {
- // treat `+0` vs. `-0` as not equal
- return a !== 0 || (1 / a == 1 / b);
- }
- // compare [[Class]] names
- var className = toString.call(a);
- if (className != toString.call(b)) {
- return false;
- }
- switch (className) {
- case boolClass:
- case dateClass:
- // coerce dates and booleans to numbers, dates to milliseconds and booleans
- // to `1` or `0`, treating invalid dates coerced to `NaN` as not equal
- return +a == +b;
- case numberClass:
- // treat `NaN` vs. `NaN` as equal
- return a != +a
- ? b != +b
- // but treat `+0` vs. `-0` as not equal
- : (a == 0 ? (1 / a == 1 / b) : a == +b);
- case regexpClass:
- case stringClass:
- // coerce regexes to strings (http://es5.github.com/#x15.10.6.4)
- // treat string primitives and their corresponding object instances as equal
- return a == b + '';
- }
- // exit early, in older browsers, if `a` is array-like but not `b`
- var isArr = arrayLikeClasses[className];
- if (noArgsClass && !isArr && (isArr = isArguments(a)) && !isArguments(b)) {
- return false;
- }
- // exit for functions and DOM nodes
- if (!isArr && (className != objectClass || (noNodeClass && (
- (typeof a.toString != 'function' && typeof (a + '') == 'string') ||
- (typeof b.toString != 'function' && typeof (b + '') == 'string'))))) {
- return false;
- }
- // assume cyclic structures are equal
- // the algorithm for detecting cyclic structures is adapted from ES 5.1
- // section 15.12.3, abstract operation `JO` (http://es5.git