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# (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:
# ------------------------- 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._
# 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
# Establish the object that gets thrown to break out of a loop iteration.
breaker: if typeof(StopIteration) is 'undefined' then '__break__' else StopIteration
# Create a safe reference to the Underscore object forreference below.
_: root._: obj => new wrapper(obj)
# Export the Underscore object for CommonJS.
if typeof(exports) != 'undefined' then exports._: _
# Create quick reference variables for speed access to core prototypes.
slice: Array::slice
unshift: Array::unshift
toString: Object::toString
hasOwnProperty: Object::hasOwnProperty
propertyIsEnumerable: Object::propertyIsEnumerable
# Current version.
_.VERSION: '0.5.5'
# ------------------------ Collection Functions: ---------------------------
# The cornerstone, an each implementation.
# Handles objects implementing forEach, arrays, and raw objects.
_.each: obj, iterator, context =>
index: 0
return obj.forEach(iterator, context) if obj.forEach
if _.isArray(obj) or _.isArguments(obj)
return, obj[i], i, obj) for i in [0...obj.length], val, key, obj) for key, val ino 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. obj, iterator, context =>
return, context) if (obj and _.isFunction(
results: []
_.each(obj) value, index, list =>
results.push(, 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, memo, iterator, context =>
return obj.reduce(_.bind(iterator, context), memo) if (obj and _.isFunction(obj.reduce))
_.each(obj) value, index, list =>
memo:, 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, memo, iterator, context =>
return obj.reduceRight(_.bind(iterator, context), memo) if (obj and _.isFunction(obj.reduceRight))
_.each(_.clone(_.toArray(obj)).reverse()) value, index =>
memo:, memo, value, index, obj)
# Return the first value which passes a truth test.
_.detect: obj, iterator, context =>
result: null
_.each(obj) value, index, list =>
if, value, index, list)
result: value
# Return all the elements that pass a truth test. Use JavaScript 1.6's
# filter(), if it exists. obj, iterator, context =>
if obj and _.isFunction(obj.filter) then return obj.filter(iterator, context)
results: []
_.each(obj) value, index, list =>
results.push(value) if, 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, value, index, list)
# Determine whether all of the elements match a truth test. Delegate to
# JavaScript 1.6's every(), if it is present.
_.all: obj, iterator, context =>
iterator ||= _.identity
return obj.every(iterator, context) if obj and _.isFunction(obj.every)
result: true
_.each(obj) value, index, list =>
_.breakLoop() unless (result: result and, 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.
_.any: obj, iterator, context =>
iterator ||= _.identity
return obj.some(iterator, context) if obj and _.isFunction(obj.some)
result: false
_.each(obj) value, index, list =>
_.breakLoop() if (result:, 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 _.isArray(obj)
for key, val ino obj
return true if val is target
# Invoke a method with arguments on every item in a collection.
_.invoke: obj, method =>
args:, 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 =>, (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, 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, value, index, list) else value
computed < result.computed and (result: {value: value, computed: computed})
# Sort the object's values by a criteria produced by an iterator.
_.sortBy: obj, iterator, context =>
_.pluck((( value, index, list =>
{value: value, criteria:, 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 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
_.first: array, n, guard =>
if n and not guard then, 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 array, index, guard =>, 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 => array[i] for i in [0...array.length] when array[i]
# Return a completely flattened version of an array.
_.flatten: array =>
_.reduce(array, []) memo, value =>
return memo.concat(_.flatten(value)) if _.isArray(value)
# Return a version of the array that does not contain the specified value(s).
_.without: array =>
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: item =>
_.all(rest) other =>
_.indexOf(other, item) >= 0
# Zip together multiple lists into a single array -- elements that share
# an index go together. =>
args: _.toArray(arguments)
length: _.max(_.pluck(args, 'length'))
results: new Array(length)
for i in [0...length]
results[i]: _.pluck(args, 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 occurence 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 array.indexOf
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 array.lastIndexOf
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. See:
_.range: start, stop, step =>
a: _.toArray(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
while true
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:, 2)
=> func.apply(obj or root, args.concat(_.toArray(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 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:, 2)
setTimeout((=> func.apply(func, args)), wait)
# Defers a function, scheduling it to run after the current call stack has
# cleared.
_.defer: func =>
_.delay.apply(_, [func, 1].concat(
# 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(_.toArray(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: _.toArray(arguments)
args: _.toArray(arguments)
for i in [(funcs.length - 1)..0]
args: [funcs[i].apply(this, args)]
# ------------------------- Object Functions: ----------------------------
# Retrieve the names of an object's properties.
_.keys: obj =>
return _.range(0, obj.length) if _.isArray(obj)
key for key, val ino obj
# Retrieve the values of an object's properties.
_.values: obj =>, _.identity)
# Return a sorted list of the function names available in Underscore.
_.functions: obj =>, key => _.isFunction(obj[key])).sort()
# Extend a given object with all of the properties in a source object.
_.extend: destination, source =>
for key, val ino source
destination[key]: val
# 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 =>
# 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 true if _.isNaN(a) and _.isNaN(b)
# Compare regular expressions.
if _.isRegExp(a) and _.isRegExp(b)
return a.source is b.source and is 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.
# for (var key in a) if (!_.isEqual(a[key], b[key])) return false;
return true
# Is a given array or object empty?
_.isEmpty: obj => _.keys(obj).length is 0
# Is a given value a DOM element?
_.isElement: obj => obj and obj.nodeType is 1
# Is a given value an array?
_.isArray: obj => !!(obj and obj.concat and obj.unshift)
# Is a given variable an arguments object?
_.isArguments: obj => obj and _.isNumber(obj.length) and !_.isArray(obj) and !, 'length')
# Is the given value a function?
_.isFunction: obj => !!(obj and obj.constructor and 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 => is '[object Number]'
# 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
# Break out of the middle of an iteration.
_.breakLoop: => throw breaker
# Generate a unique integer id (unique within the entire client session).
# Useful for temporary DOM ids.
idCounter: 0
_.uniqueId: prefix =>
(prefix or '') + idCounter++
# JavaScript templating a-la ERB, pilfered from John Resig's
# "Secrets of the JavaScript Ninja", page 83.
_.template: str, data =>
`var fn = new Function('obj',
'var p=[],print=function(){p.push.apply(p,arguments);};' +
'with(obj){p.push(\'' +
replace(/[\r\t\n]/g, " ").
replace(/((^|%>)[^\t]*)'/g, "$1\r").
replace(/\t=(.*?)%>/g, "',$1,'").
split("\r").join("\\'") +
"');}return p.join('');")`
if data then fn(data) else fn
# ------------------------------- Aliases ----------------------------------
_.forEach: _.each
_.foldl: _.inject: _.reduce
_.foldr: _.reduceRight
_.every: _.all
_.some: _.any
_.head: _.first
_.methods: _.functions
# /*------------------------ Setup the OOP Wrapper: --------------------------*/
# Helper function to continue chaining intermediate results.
result: obj, chain =>
if chain then _(obj).chain() else obj
# Add all of the Underscore functions to the wrapper object.
_.each(_.functions(_)) name =>
method: _[name]
wrapper.prototype[name]: =>
args: _.toArray(arguments), this._wrapped)
result(method.apply(_, args), this._chain)
# 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
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