underscore.js

// Underscore.js
// (c) 2009 Jeremy Ashkenas, DocumentCloud Inc.
// Underscore is freely distributable under the terms of the MIT license.
// Portions of Underscore are inspired by or borrowed from Prototype.js, 
// Oliver Steele's Functional, and John Resig's Micro-Templating.
// For all details and documentation:
// http://documentcloud.github.com/underscore/

(function() {
  
  /*------------------------- Baseline setup ---------------------------------*/
  
  // Establish the root object, "window" in the browser, or "global" on the server.
  var root = this;
  
  // Save the previous value of the "_" variable.
  var previousUnderscore = root._;
  
  // If Underscore is called as a function, it returns a wrapped object that
  // can be used OO-style. This wrapper holds altered versions of all the 
  // underscore functions. Wrapped objects may be chained.
  var wrapper = function(obj) { this._wrapped = obj; };
  
  // Create a safe reference to the Underscore object for reference below.
  var _ = root._ = function(obj) { return new wrapper(obj); };
  
  // Export the Underscore object for CommonJS.
  if (typeof exports !== 'undefined') _ = exports;
  
  // Current version.
  _.VERSION = '0.4.0';  
  
  /*------------------------ Collection Functions: ---------------------------*/
    
  // The cornerstone, an each implementation.
  // Handles objects implementing forEach, each, arrays, and raw objects.
  _.each = function(obj, iterator, context) {
    var index = 0;
    try {
      if (obj.forEach) {
        obj.forEach(iterator, context);
      } else if (obj.length) {
        for (var i=0, l = obj.length; i<l; i++) iterator.call(context, obj[i], i, obj);
      } else if (obj.each) {
        obj.each(function(value) { iterator.call(context, value, index++, obj); });
      } else {
        for (var key in obj) if (Object.prototype.hasOwnProperty.call(obj, key)) {
          iterator.call(context, obj[key], key, obj);
        }
      }
    } catch(e) {
      if (e != '__break__') throw e;
    }
    return obj;
  };
  
  // Return the results of applying the iterator to each element. Use JavaScript
  // 1.6's version of map, if possible.
  _.map = function(obj, iterator, context) {
    if (obj && obj.map) return obj.map(iterator, context);
    var results = [];
    _.each(obj, function(value, index, list) {
      results.push(iterator.call(context, value, index, list));
    });
    return results;
  };
  
  // Reduce builds up a single result from a list of values. Also known as
  // inject, or foldl. Uses JavaScript 1.8's version of reduce, if possible.
  _.reduce = function(obj, memo, iterator, context) {
    if (obj && obj.reduce) return obj.reduce(_.bind(iterator, context), memo);
    _.each(obj, function(value, index, list) {
      memo = iterator.call(context, memo, value, index, list);
    });
    return memo;
  };
  
  // The right-associative version of reduce, also known as foldr. Uses 
  // JavaScript 1.8's version of reduceRight, if available.
  _.reduceRight = function(obj, memo, iterator, context) {
    if (obj && obj.reduceRight) return obj.reduceRight(_.bind(iterator, context), memo);
    var reversed = _.clone(_.toArray(obj)).reverse();
    _.each(reversed, function(value, index) {
      memo = iterator.call(context, memo, value, index, obj);
    });
    return memo;
  };
  
  // Return the first value which passes a truth test.
  _.detect = function(obj, iterator, context) {
    var result;
    _.each(obj, function(value, index, list) {
      if (iterator.call(context, value, index, list)) {
        result = value;
        throw '__break__';
      }
    });
    return result;
  };
  
  // Return all the elements that pass a truth test. Use JavaScript 1.6's
  // filter(), if it exists.
  _.select = function(obj, iterator, context) {
    if (obj.filter) return obj.filter(iterator, context);
    var results = [];
    _.each(obj, function(value, index, list) {
      iterator.call(context, value, index, list) && results.push(value);
    });
    return results;
  };
  
  // Return all the elements for which a truth test fails.
  _.reject = function(obj, iterator, context) {
    var results = [];
    _.each(obj, function(value, index, list) {
      !iterator.call(context, value, index, list) && results.push(value);
    });
    return results;
  };
  
  // Determine whether all of the elements match a truth test. Delegate to
  // JavaScript 1.6's every(), if it is present.
  _.all = function(obj, iterator, context) {
    iterator = iterator || _.identity;
    if (obj.every) return obj.every(iterator, context);
    var result = true;
    _.each(obj, function(value, index, list) {
      if (!(result = result && iterator.call(context, value, index, list))) throw '__break__';
    });
    return result;
  };
  
  // Determine if at least one element in the object matches a truth test. Use
  // JavaScript 1.6's some(), if it exists.
  _.any = function(obj, iterator, context) {
    iterator = iterator || _.identity;
    if (obj.some) return obj.some(iterator, context);
    var result = false;
    _.each(obj, function(value, index, list) {
      if (result = iterator.call(context, value, index, list)) throw '__break__';
    });
    return result;
  };
  
  // Determine if a given value is included in the array or object, 
  // based on '==='.
  _.include = function(obj, target) {
    if (_.isArray(obj)) return _.indexOf(obj, target) != -1;
    var found = false;
    _.each(obj, function(value) {
      if (found = value === target) {
        throw '__break__';
      }
    });
    return found;
  };
  
  // Invoke a method with arguments on every item in a collection.
  _.invoke = function(obj, method) {
    var args = _.toArray(arguments).slice(2);
    return _.map(obj, function(value) {
      return (method ? value[method] : value).apply(value, args);
    });
  };
  
  // Convenience version of a common use case of map: fetching a property.
  _.pluck = function(obj, key) {
    return _.map(obj, function(value){ return value[key]; });
  };
  
  // Return the maximum item or (item-based computation).
  _.max = function(obj, iterator, context) {
    if (!iterator && _.isArray(obj)) return Math.max.apply(Math, obj);
    var result = {computed : -Infinity};
    _.each(obj, function(value, index, list) {
      var computed = iterator ? iterator.call(context, value, index, list) : value;
      computed >= result.computed && (result = {value : value, computed : computed});
    });
    return result.value;
  };
  
  // Return the minimum element (or element-based computation).
  _.min = function(obj, iterator, context) {
    if (!iterator && _.isArray(obj)) return Math.min.apply(Math, obj);
    var result = {computed : Infinity};
    _.each(obj, function(value, index, list) {
      var computed = iterator ? iterator.call(context, value, index, list) : value;
      computed < result.computed && (result = {value : value, computed : computed});
    });
    return result.value;
  };
  
  // Sort the object's values by a criteria produced by an iterator.
  _.sortBy = function(obj, iterator, context) {
    return _.pluck(_.map(obj, function(value, index, list) {
      return {
        value : value,
        criteria : iterator.call(context, value, index, list)
      };
    }).sort(function(left, right) {
      var a = left.criteria, b = right.criteria;
      return a < b ? -1 : a > b ? 1 : 0;
    }), 'value');
  };
  
  // Use a comparator function to figure out at what index an object should
  // be inserted so as to maintain order. Uses binary search.
  _.sortedIndex = function(array, obj, iterator) {
    iterator = iterator || _.identity;
    var low = 0, high = array.length;
    while (low < high) {
      var mid = (low + high) >> 1;
      iterator(array[mid]) < iterator(obj) ? low = mid + 1 : high = mid;
    }
    return low;
  };
  
  // Convert anything iterable into a real, live array.
  _.toArray = function(iterable) {
    if (!iterable) return [];
    if (_.isArray(iterable)) return iterable;
    return _.map(iterable, function(val){ return val; });
  };
  
  // Return the number of elements in an object.
  _.size = function(obj) {
    return _.toArray(obj).length;
  };
  
  /*-------------------------- Array Functions: ------------------------------*/
  
  // Get the first element of an array.
  _.first = function(array) {
    return array[0];
  };
  
  // Get the last element of an array.
  _.last = function(array) {
    return array[array.length - 1];
  };
  
  // Trim out all falsy values from an array.
  _.compact = function(array) {
    return _.select(array, function(value){ return !!value; });
  };
  
  // Return a completely flattened version of an array.
  _.flatten = function(array) {
    return _.reduce(array, [], function(memo, value) {
      if (_.isArray(value)) return memo.concat(_.flatten(value));
      memo.push(value);
      return memo;
    });
  };
  
  // Return a version of the array that does not contain the specified value(s).
  _.without = function(array) {
    var values = array.slice.call(arguments, 0);
    return _.select(array, function(value){ return !_.include(values, value); });
  };
  
  // Produce a duplicate-free version of the array. If the array has already
  // been sorted, you have the option of using a faster algorithm.
  _.uniq = function(array, isSorted) {
    return _.reduce(array, [], function(memo, el, i) {
      if (0 == i || (isSorted ? _.last(memo) != el : !_.include(memo, el))) memo.push(el);
      return memo;
    });
  };
  
  // Produce an array that contains every item shared between all the 
  // passed-in arrays.
  _.intersect = function(array) {
    var rest = _.toArray(arguments).slice(1);
    return _.select(_.uniq(array), function(item) {
      return _.all(rest, function(other) { 
        return _.indexOf(other, item) >= 0;
      });
    });
  };
  
  // Zip together multiple lists into a single array -- elements that share
  // an index go together.
  _.zip = function() {
    var args = _.toArray(arguments);
    var length = _.max(_.pluck(args, 'length'));
    var results = new Array(length);
    for (var i=0; i<length; i++) results[i] = _.pluck(args, String(i));
    return results;
  };
  
  // If the browser doesn't supply us with indexOf (I'm looking at you, MSIE), 
  // we need this function. Return the position of the first occurence of an 
  // item in an array, or -1 if the item is not included in the array.
  _.indexOf = function(array, item) {
    if (array.indexOf) return array.indexOf(item);
    for (i=0, l=array.length; i<l; i++) if (array[i] === item) return i;
    return -1;
  };
  
  // Provide JavaScript 1.6's lastIndexOf, delegating to the native function,
  // if possible.
  _.lastIndexOf = function(array, item) {
    if (array.lastIndexOf) return array.lastIndexOf(item);
    var i = array.length;
    while (i--) if (array[i] === item) return i;
    return -1;
  };
  
  /* ----------------------- Function Functions: -----------------------------*/
  
  // Create a function bound to a given object (assigning 'this', and arguments,
  // optionally). Binding with arguments is also known as 'curry'.
  _.bind = function(func, context) {
    if (!context) return func;
    var args = _.toArray(arguments).slice(2);
    return function() {
      var a = args.concat(_.toArray(arguments));
      return func.apply(context, a);
    };
  };
  
  // Bind all of an object's methods to that object. Useful for ensuring that 
  // all callbacks defined on an object belong to it.
  _.bindAll = function() {
    var args = _.toArray(arguments);
    var context = args.pop();
    _.each(args, function(methodName) {
      context[methodName] = _.bind(context[methodName], context);
    });
  };
  
  // Delays a function for the given number of milliseconds, and then calls
  // it with the arguments supplied.
  _.delay = function(func, wait) {
    var args = _.toArray(arguments).slice(2);
    return setTimeout(function(){ return func.apply(func, args); }, wait);
  };
  
  // Defers a function, scheduling it to run after the current call stack has 
  // cleared.
  _.defer = function(func) {
    return _.delay.apply(_, [func, 1].concat(_.toArray(arguments).slice(1)));
  };
  
  // Returns the first function passed as an argument to the second, 
  // allowing you to adjust arguments, run code before and after, and 
  // conditionally execute the original function.
  _.wrap = function(func, wrapper) {
    return function() {
      var args = [func].concat(_.toArray(arguments));
      return wrapper.apply(wrapper, args);
    };
  };
  
  // Returns a function that is the composition of a list of functions, each
  // consuming the return value of the function that follows.
  _.compose = function() {
    var funcs = _.toArray(arguments);
    return function() {
      for (var i=funcs.length-1; i >= 0; i--) {
        arguments = [funcs[i].apply(this, arguments)];
      }
      return arguments[0];
    };
  };
  
  /* ------------------------- Object Functions: ---------------------------- */
  
  // Retrieve the names of an object's properties.
  _.keys = function(obj) {
    return _.map(obj, function(value, key){ return key; });
  };
  
  // Retrieve the values of an object's properties.
  _.values = function(obj) {
    return _.map(obj, _.identity);
  };
  
  // Extend a given object with all of the properties in a source object.
  _.extend = function(destination, source) {
    for (var property in source) destination[property] = source[property];
    return destination;
  };
  
  // Create a (shallow-cloned) duplicate of an object.
  _.clone = function(obj) {
    if (_.isArray(obj)) return obj.slice(0);
    return _.extend({}, obj);
  };
  
  // Perform a deep comparison to check if two objects are equal.
  _.isEqual = function(a, b) {
    // Check object identity.
    if (a === b) return true;
    // Different types?
    var atype = typeof(a), btype = typeof(b);
    if (atype != btype) return false;
    // Basic equality test (watch out for coercions).
    if (a == b) return true;
    // One of them implements an isEqual()?
    if (a.isEqual) return a.isEqual(b);
    // If a is not an object by this point, we can't handle it.
    if (atype !== 'object') return false;
    // Nothing else worked, deep compare the contents.
    var aKeys = _.keys(a), bKeys = _.keys(b);
    // Different object sizes?
    if (aKeys.length != bKeys.length) return false;
    // Recursive comparison of contents.
    for (var key in a) if (!_.isEqual(a[key], b[key])) return false;
    return true;
  };
  
  // Is a given value a DOM element?
  _.isElement = function(obj) {
    return !!(obj && obj.nodeType == 1);
  };
  
  // Is a given value a real Array?
  _.isArray = function(obj) {
    return Object.prototype.toString.call(obj) == '[object Array]';
  };
  
  // Is a given value a Function?
  _.isFunction = function(obj) {
    return Object.prototype.toString.call(obj) == '[object Function]';
  };
  
  // Is a given variable undefined?
  _.isUndefined = function(obj) {
    return typeof obj == 'undefined';
  };
  
  /* -------------------------- Utility Functions: -------------------------- */
  
  // Run Underscore.js in noConflict mode, returning the '_' variable to its
  // previous owner. Returns a reference to the Underscore object.
  _.noConflict = function() {
    root._ = previousUnderscore;
    return this;
  };
  
  // Keep the identity function around for default iterators.
  _.identity = function(value) { 
    return value;
  };
  
  // Generate a unique integer id (unique within the entire client session).
  // Useful for temporary DOM ids.
  var idCounter = 0;
  _.uniqueId = function(prefix) {
    var id = idCounter++;
    return prefix ? prefix + id : id;
  };
  
  // Return a sorted list of the function names available in Underscore.
  _.functions = function() {
    var functions = [];
    for (var key in _) if (Object.prototype.hasOwnProperty.call(_, key)) functions.push(key);
    return _.without(functions, 'VERSION', 'prototype', 'noConflict').sort();
  };
  
  // JavaScript templating a-la ERB, pilfered from John Resig's 
  // "Secrets of the JavaScript Ninja", page 83.
  _.template = function(str, data) {
    var fn = new Function('obj', 
      'var p=[],print=function(){p.push.apply(p,arguments);};' +
      'with(obj){p.push(\'' +
      str
        .replace(/[\r\t\n]/g, " ") 
        .split("<%").join("\t") 
        .replace(/((^|%>)[^\t]*)'/g, "$1\r") 
        .replace(/\t=(.*?)%>/g, "',$1,'") 
        .split("\t").join("');") 
        .split("%>").join("p.push('") 
        .split("\r").join("\\'") 
    + "');}return p.join('');");
    return data ? fn(data) : fn;  
  };
  
  /*------------------------------- Aliases ----------------------------------*/

  _.forEach  = _.each;
  _.foldl    = _.inject       = _.reduce;
  _.foldr    = _.reduceRight;
  _.filter   = _.select;
  _.every    = _.all;
  _.some     = _.any;
  _.methods  = _.functions;
  
  /*------------------------ Setup the OOP Wrapper: --------------------------*/
  
  // Add all of the Underscore functions to the wrapper object.
  _.each(_.functions(), function(name) {
    wrapper.prototype[name] = function() {
      Array.prototype.unshift.call(arguments, this._wrapped);
      var result = _[name].apply(_, arguments);
      return this._chain ? _(result).chain() : result;
    };
  });
  
  // Start chaining a wrapped Underscore object.
  wrapper.prototype.chain = function() {
    this._chain = true;
    return this;
  };
  
  // Extracts the result from a wrapped and chained object.
  wrapper.prototype.get = function() {
    return this._wrapped;
  };

})();