# underscore.coffee

¶

Underscore.coffee (c) 2010 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) ->
      try
        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]
        else
          iterator.call context, val, key, obj  for key, val of obj
      catch e
        throw e if e isnt breaker
      obj

¶

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
      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 = (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
      memo

¶

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
          _.breakLoop()
      result

¶

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
      results

¶

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
      results

¶

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))
      result

¶

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))
      result

¶

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
      for key, val of obj
        return true if val is target
      false

¶

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})
      result.value

¶

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})
      result.value

¶

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
      low

¶

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))
      _.values(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
        memo
      , []

¶

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))
      memo

¶

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
      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 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++
      -1

¶

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--
      -1

¶

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
      loop
        return range if (if step > 0 then i - stop else stop - i) >= 0
        range[idx] = i
        idx++
        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
      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)]
        args[0]

¶

## 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
      obj

¶

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
      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 all key, val of a when !(key of b) or !_.isEqual(val, b[key])
      true

¶

Is a given array or object empty?

    _.isEmpty = (obj) ->
      return obj.length is 0 if _.isArray(obj) or _.isString(obj)
      return false for key of obj when hasOwnProperty.call(obj, key)
      true

¶

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
      this

¶

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(endMatch,"✄")
           .split("'").join("\\'")
           .split("✄").join("'")
           .replace(c.interpolate, "',$1,'")
           .split(c.start).join("');")
           .split(c.end).join("p.push('") +
           "');}return p.join('');"
      if data then fn(data) else fn

¶

## Aliases

    _.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
      this

¶

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 of the 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
      this

¶

Extracts the result from a wrapped and chained object.

    wrapper::value = -> this._wrapped