function extend(destination, source) {
    for (var property in source) {
        destination[property] = source[property];
    }
    return destination;
}

Array.prototype.sum = function() {
    var result = 0;
    for (var i = 0; i < this.length; i++) {
        result += this[i];
    }
};

if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function(elt /*, from*/) {
        var len = this.length >>> 0;

        var from = Number(arguments[1]) || 0;
        from = (from < 0) ? Math.ceil(from) : Math.floor(from);
        if (from < 0) {
            from += len;
        }
        for (; from < len; from++) {
            if (from in this && this[from] === elt) {
                return from;
            }
        }
        return -1;
    };
};