Underscore.coffee (c) 2011 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/

Baseline setup

Establish the root object, window in the browser, or global on the server.

root = this

Save the previous value of the _ variable.

previousUnderscore = root._

Establish the object that gets thrown to break out of a loop iteration. StopIteration is SOP on Mozilla.

breaker = if typeof(StopIteration) is 'undefined' then '__break__' else StopIteration

Helper function to escape RegExp contents, because JS doesn't have one.

escapeRegExp = (string) -> string.replace(/([.*+?^${}()|[\]\/\\])/g, '\\$1')

Save bytes in the minified (but not gzipped) version:

ArrayProto           = Array.prototype
ObjProto             = Object.prototype

Create quick reference variables for speed access to core prototypes.

slice                = ArrayProto.slice
unshift              = ArrayProto.unshift
toString             = ObjProto.toString
hasOwnProperty       = ObjProto.hasOwnProperty
propertyIsEnumerable = ObjProto.propertyIsEnumerable

All ECMA5 native implementations we hope to use are declared here.

nativeForEach        = ArrayProto.forEach
nativeMap            = ArrayProto.map
nativeReduce         = ArrayProto.reduce
nativeReduceRight    = ArrayProto.reduceRight
nativeFilter         = ArrayProto.filter
nativeEvery          = ArrayProto.every
nativeSome           = ArrayProto.some
nativeIndexOf        = ArrayProto.indexOf
nativeLastIndexOf    = ArrayProto.lastIndexOf
nativeIsArray        = Array.isArray
nativeKeys           = Object.keys

Create a safe reference to the Underscore object for use below.

_ = (obj) -> new wrapper(obj)

Export the Underscore object for CommonJS.

if typeof(exports) != 'undefined' then exports._ = _

Export Underscore to global scope.

root._ = _

Current version.

_.VERSION = '1.1.0'

Collection Functions

The cornerstone, an each implementation. Handles objects implementing forEach, arrays, and raw objects.

_.each = (obj, iterator, context) ->
    if nativeForEach and obj.forEach is nativeForEach
      obj.forEach iterator, context
    else if _.isNumber obj.length
      iterator.call context, obj[i], i, obj for i in [0...obj.length]
      iterator.call context, val, key, obj  for own key, val of obj
  catch e
    throw e if e isnt breaker

Return the results of applying the iterator to each element. Use JavaScript 1.6's version of map, if possible.

_.map = (obj, iterator, context) ->
  return obj.map(iterator, context) if nativeMap and obj.map is nativeMap
  results = []
  _.each obj, (value, index, list) ->
    results.push iterator.call context, value, index, list

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 = (obj, iterator, memo, context) ->
  if nativeReduce and obj.reduce is nativeReduce
    iterator = _.bind iterator, context if context
    return obj.reduce iterator, memo
  _.each obj, (value, index, list) ->
    memo = iterator.call context, memo, value, index, list

The right-associative version of reduce, also known as foldr. Uses JavaScript 1.8's version of reduceRight, if available.

_.reduceRight = (obj, iterator, memo, context) ->
  if nativeReduceRight and obj.reduceRight is nativeReduceRight
    iterator = _.bind iterator, context if context
    return obj.reduceRight iterator, memo
  reversed = _.clone(_.toArray(obj)).reverse()
  _.reduce reversed, iterator, memo, context

Return the first value which passes a truth test.

_.detect = (obj, iterator, context) ->
  result = null
  _.each obj, (value, index, list) ->
    if iterator.call context, value, index, list
      result = value

Return all the elements that pass a truth test. Use JavaScript 1.6's filter, if it exists.

_.filter = (obj, iterator, context) ->
  return obj.filter iterator, context if nativeFilter and obj.filter is nativeFilter
  results = []
  _.each obj, (value, index, list) ->
    results.push value if iterator.call context, value, index, list

Return all the elements for which a truth test fails.

_.reject = (obj, iterator, context) ->
  results = []
  _.each obj, (value, index, list) ->
    results.push value if not iterator.call context, value, index, list

Determine whether all of the elements match a truth test. Delegate to JavaScript 1.6's every, if it is present.

_.every = (obj, iterator, context) ->
  iterator ||= _.identity
  return obj.every iterator, context if nativeEvery and obj.every is nativeEvery
  result = true
  _.each obj, (value, index, list) ->
    _.breakLoop() unless (result = result and iterator.call(context, value, index, list))

Determine if at least one element in the object matches a truth test. Use JavaScript 1.6's some, if it exists.

_.some = (obj, iterator, context) ->
  iterator ||= _.identity
  return obj.some iterator, context if nativeSome and obj.some is nativeSome
  result = false
  _.each obj, (value, index, list) ->
    _.breakLoop() if (result = iterator.call(context, value, index, list))

Determine if a given value is included in the array or object, based on ===.

_.include = (obj, target) ->
  return _.indexOf(obj, target) isnt -1 if nativeIndexOf and obj.indexOf is nativeIndexOf
  return true for own key, val of obj when val is target

Invoke a method with arguments on every item in a collection.

_.invoke = (obj, method) ->
  args = _.rest arguments, 2
  (if method then val[method] else val).apply(val, args) for val in obj

Convenience version of a common use case of map: fetching a property.

_.pluck = (obj, key) ->
  _.map(obj, (val) -> val[key])

Return the maximum item or (item-based computation).

_.max = (obj, iterator, context) ->
  return Math.max.apply(Math, obj) if not iterator and _.isArray(obj)
  result = computed: -Infinity
  _.each obj, (value, index, list) ->
    computed = if iterator then iterator.call(context, value, index, list) else value
    computed >= result.computed and (result = {value: value, computed: computed})

Return the minimum element (or element-based computation).

_.min = (obj, iterator, context) ->
  return Math.min.apply(Math, obj) if not iterator and _.isArray(obj)
  result = computed: Infinity
  _.each obj, (value, index, list) ->
    computed = if iterator then iterator.call(context, value, index, list) else value
    computed < result.computed and (result = {value: value, computed: computed})

Sort the object's values by a criterion produced by an iterator.

_.sortBy = (obj, iterator, context) ->
  _.pluck(((_.map obj, (value, index, list) ->
    {value: value, criteria: iterator.call(context, value, index, list)}
  ).sort((left, right) ->
    a = left.criteria; b = right.criteria
    if a < b then -1 else if a > b then 1 else 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 = (array, obj, iterator) ->
  iterator ||= _.identity
  low =  0
  high = array.length
  while low < high
    mid = (low + high) >> 1
    if iterator(array[mid]) < iterator(obj) then low = mid + 1 else high = mid

Convert anything iterable into a real, live array.

_.toArray = (iterable) ->
  return []                   if (!iterable)
  return iterable.toArray()   if (iterable.toArray)
  return iterable             if (_.isArray(iterable))
  return slice.call(iterable) if (_.isArguments(iterable))

Return the number of elements in an object.

_.size = (obj) -> _.toArray(obj).length

Array Functions

Get the first element of an array. Passing n will return the first N values in the array. Aliased as head. The guard check allows it to work with map.

_.first = (array, n, guard) ->
  if n and not guard then slice.call(array, 0, n) else array[0]

Returns everything but the first entry of the array. Aliased as tail. Especially useful on the arguments object. Passing an index will return the rest of the values in the array from that index onward. The guard check allows it to work with map.

_.rest = (array, index, guard) ->
  slice.call(array, if _.isUndefined(index) or guard then 1 else index)

Get the last element of an array.

_.last = (array) -> array[array.length - 1]

Trim out all falsy values from an array.

_.compact = (array) -> item for item in array when item

Return a completely flattened version of an array.

_.flatten = (array) ->
  _.reduce array, (memo, value) ->
    return memo.concat(_.flatten(value)) if _.isArray value
    memo.push value
  , []

Return a version of the array that does not contain the specified value(s).

_.without = (array) ->
  values = _.rest arguments
  val for val in _.toArray(array) when not _.include values, val

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 = (array, isSorted) ->
  memo = []
  for el, i in _.toArray array
    memo.push el if i is 0 || (if isSorted is true then _.last(memo) isnt el else not _.include(memo, el))

Produce an array that contains every item shared between all the passed-in arrays.

_.intersect = (array) ->
  rest = _.rest arguments
  _.select _.uniq(array), (item) ->
    _.all rest, (other) ->
      _.indexOf(other, item) >= 0

Zip together multiple lists into a single array -- elements that share an index go together.

_.zip = ->
  length =  _.max _.pluck arguments, 'length'
  results = new Array length
  for i in [0...length]
    results[i] = _.pluck arguments, String i

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 occurrence of an item in an array, or -1 if the item is not included in the array.

_.indexOf = (array, item) ->
  return array.indexOf item if nativeIndexOf and array.indexOf is nativeIndexOf
  i = 0; l = array.length
  while l - i
    if array[i] is item then return i else i++

Provide JavaScript 1.6's lastIndexOf, delegating to the native function, if possible.

_.lastIndexOf = (array, item) ->
  return array.lastIndexOf(item) if nativeLastIndexOf and array.lastIndexOf is nativeLastIndexOf
  i = array.length
  while i
    if array[i] is item then return i else i--

Generate an integer Array containing an arithmetic progression. A port of the native Python range function.

_.range = (start, stop, step) ->
  a         = arguments
  solo      = a.length <= 1
  i = start = if solo then 0 else a[0]
  stop      = if solo then a[0] else a[1]
  step      = a[2] or 1
  len       = Math.ceil((stop - start) / step)
  return []   if len <= 0
  range     = new Array len
  idx       = 0
    return range if (if step > 0 then i - stop else stop - i) >= 0
    range[idx] = i
    i+= step

Function Functions

Create a function bound to a given object (assigning this, and arguments, optionally). Binding with arguments is also known as curry.

_.bind = (func, obj) ->
  args = _.rest arguments, 2
  -> func.apply obj or root, args.concat arguments

Bind all of an object's methods to that object. Useful for ensuring that all callbacks defined on an object belong to it.

_.bindAll = (obj) ->
  funcs = if arguments.length > 1 then _.rest(arguments) else _.functions(obj)
  _.each funcs, (f) -> obj[f] = _.bind obj[f], obj

Delays a function for the given number of milliseconds, and then calls it with the arguments supplied.

_.delay = (func, wait) ->
  args = _.rest arguments, 2
  setTimeout((-> func.apply(func, args)), wait)

Memoize an expensive function by storing its results.

_.memoize = (func, hasher) ->
  memo = {}
  hasher or= _.identity
    key = hasher.apply this, arguments
    return memo[key] if key of memo
    memo[key] = func.apply this, arguments

Defers a function, scheduling it to run after the current call stack has cleared.

_.defer = (func) ->
  _.delay.apply _, [func, 1].concat _.rest arguments

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 = (func, wrapper) ->
  -> wrapper.apply wrapper, [func].concat arguments

Returns a function that is the composition of a list of functions, each consuming the return value of the function that follows.

_.compose = ->
  funcs = arguments
    args = arguments
    for i in [funcs.length - 1..0] by -1
      args = [funcs[i].apply(this, args)]

Object Functions

Retrieve the names of an object's properties.

_.keys = nativeKeys or (obj) ->
  return _.range 0, obj.length if _.isArray(obj)
  key for key, val of obj

Retrieve the values of an object's properties.

_.values = (obj) ->
  _.map obj, _.identity

Return a sorted list of the function names available in Underscore.

_.functions = (obj) ->
  _.filter(_.keys(obj), (key) -> _.isFunction(obj[key])).sort()

Extend a given object with all of the properties in a source object.

_.extend = (obj) ->
  for source in _.rest(arguments)
    obj[key] = val for key, val of source

Create a (shallow-cloned) duplicate of an object.

_.clone = (obj) ->
  return obj.slice 0 if _.isArray obj
  _.extend {}, obj

Invokes interceptor with the obj, and then returns obj. The primary purpose of this method is to "tap into" a method chain, in order to perform operations on intermediate results within the chain.

_.tap = (obj, interceptor) ->
  interceptor obj

Perform a deep comparison to check if two objects are equal.

_.isEqual = (a, b) ->

Check object identity.

  return true if a is b

Different types?

  atype = typeof(a); btype = typeof(b)
  return false if atype isnt btype

Basic equality test (watch out for coercions).

  return true if `a == b`

One is falsy and the other truthy.

  return false if (!a and b) or (a and !b)

One of them implements an isEqual()?

  return a.isEqual(b) if a.isEqual

Check dates' integer values.

  return a.getTime() is b.getTime() if _.isDate(a) and _.isDate(b)

Both are NaN?

  return false if _.isNaN(a) and _.isNaN(b)

Compare regular expressions.

  if _.isRegExp(a) and _.isRegExp(b)
    return a.source     is b.source and
           a.global     is b.global and
           a.ignoreCase is b.ignoreCase and
           a.multiline  is b.multiline

If a is not an object by this point, we can't handle it.

  return false if atype isnt 'object'

Check for different array lengths before comparing contents.

  return false if a.length and (a.length isnt b.length)

Nothing else worked, deep compare the contents.

  aKeys = _.keys(a); bKeys = _.keys(b)

Different object sizes?

  return false if aKeys.length isnt bKeys.length

Recursive comparison of contents.

  return false for key, val of a when !(key of b) or !_.isEqual(val, b[key])

Is a given array or object empty?

_.isEmpty = (obj) ->
  return obj.length is 0 if _.isArray(obj) or _.isString(obj)
  return false for own key of obj

Is a given value a DOM element?

_.isElement   = (obj) -> obj and obj.nodeType is 1

Is a given value an array?

_.isArray     = nativeIsArray or (obj) -> !!(obj and obj.concat and obj.unshift and not obj.callee)

Is a given variable an arguments object?

_.isArguments = (obj) -> obj and obj.callee

Is the given value a function?

_.isFunction  = (obj) -> !!(obj and obj.constructor and obj.call and obj.apply)

Is the given value a string?

_.isString    = (obj) -> !!(obj is '' or (obj and obj.charCodeAt and obj.substr))

Is a given value a number?

_.isNumber    = (obj) -> (obj is +obj) or toString.call(obj) is '[object Number]'

Is a given value a boolean?

_.isBoolean   = (obj) -> obj is true or obj is false

Is a given value a Date?

_.isDate      = (obj) -> !!(obj and obj.getTimezoneOffset and obj.setUTCFullYear)

Is the given value a regular expression?

_.isRegExp    = (obj) -> !!(obj and obj.exec and (obj.ignoreCase or obj.ignoreCase is false))

Is the given value NaN -- this one is interesting. NaN != NaN, and isNaN(undefined) == true, so we make sure it's a number first.

_.isNaN       = (obj) -> _.isNumber(obj) and window.isNaN(obj)

Is a given value equal to null?

_.isNull      = (obj) -> obj is null

Is a given variable undefined?

_.isUndefined = (obj) -> typeof obj is 'undefined'

Utility Functions

Run Underscore.js in noConflict mode, returning the _ variable to its previous owner. Returns a reference to the Underscore object.

_.noConflict = ->
  root._ = previousUnderscore

Keep the identity function around for default iterators.

_.identity = (value) -> value

Run a function n times.

_.times = (n, iterator, context) ->
  iterator.call context, i for i in [0...n]

Break out of the middle of an iteration.

_.breakLoop = -> throw breaker

Add your own custom functions to the Underscore object, ensuring that they're correctly added to the OOP wrapper as well.

_.mixin = (obj) ->
  for name in _.functions(obj)
    addToWrapper name, _[name] = obj[name]

Generate a unique integer id (unique within the entire client session). Useful for temporary DOM ids.

idCounter = 0
_.uniqueId = (prefix) ->
  (prefix or '') + idCounter++

By default, Underscore uses ERB-style template delimiters, change the following template settings to use alternative delimiters.

_.templateSettings = {
  start:        '<%'
  end:          '%>'
  interpolate:  /<%=(.+?)%>/g

JavaScript templating a-la ERB, pilfered from John Resig's Secrets of the JavaScript Ninja, page 83. Single-quote fix from Rick Strahl. With alterations for arbitrary delimiters, and to preserve whitespace.

_.template = (str, data) ->
  c = _.templateSettings
  endMatch = new RegExp("'(?=[^"+c.end.substr(0, 1)+"]*"+escapeRegExp(c.end)+")","g")
  fn = new Function 'obj',
    'var p=[],print=function(){p.push.apply(p,arguments);};' +
    'with(obj||{}){p.push(\'' +
    str.replace(/\r/g, '\\r')
       .replace(/\n/g, '\\n')
       .replace(/\t/g, '\\t')
       .replace(c.interpolate, "',$1,'")
       .split(c.end).join("p.push('") +
       "');}return p.join('');"
  if data then fn(data) else fn


_.forEach  = _.each
_.foldl    = _.inject = _.reduce
_.foldr    = _.reduceRight
_.select   = _.filter
_.all      = _.every
_.any      = _.some
_.contains = _.include
_.head     = _.first
_.tail     = _.rest
_.methods  = _.functions

Setup the OOP Wrapper

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.

wrapper = (obj) ->
  this._wrapped = obj

Helper function to continue chaining intermediate results.

result = (obj, chain) ->
  if chain then _(obj).chain() else obj

A method to easily add functions to the OOP wrapper.

addToWrapper = (name, func) ->
  wrapper.prototype[name] = ->
    args = _.toArray arguments
    unshift.call args, this._wrapped
    result func.apply(_, args), this._chain

Add all ofthe Underscore functions to the wrapper object.

_.mixin _

Add all mutator Array functions to the wrapper.

_.each ['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], (name) ->
  method = Array.prototype[name]
  wrapper.prototype[name] = ->
    method.apply(this._wrapped, arguments)
    result(this._wrapped, this._chain)

Add all accessor Array functions to the wrapper.

_.each ['concat', 'join', 'slice'], (name) ->
  method = Array.prototype[name]
  wrapper.prototype[name] = ->
    result(method.apply(this._wrapped, arguments), this._chain)

Start chaining a wrapped Underscore object.

wrapper::chain = ->
  this._chain = true

Extracts the result from a wrapped and chained object.

wrapper::value = -> this._wrapped