# array # Array utilities. ## append(arr1, arr2):Array Appends an array to the end of the other. The first array will be modified and will contain the appended items. See: [`union()`](#union), [`combine()`](#combine) ```js var foo = ['a', 'b'], bar = ['b', 'd']; append(foo, bar); // ['a', 'b', 'b', 'd'] ``` ## collect(arr, callback, [thisObj]):Array Maps the items in `arr` and concatenates the resulting arrays. See: [`map()`](#map) ```js collect([1, 2, 3], function(val) { return [val, val % 2]; }); // [1, 1, 2, 0, 3, 1]; collect(['a', 'bb', ''], function(val) { return val.split(''); }); // ['a', 'b', 'b'] ``` It also supports a shorthand syntax: ```js var items = [{ a: [1] }, { b: 'foo' }, { a: [2, 3] }]; collect(items, 'a'); // [1, 2, 3]; ``` ## combine(arr1, arr2):Array Combines an array with all the items of another. The first array will be modified and will contain the combined items. Does not allow duplicates and is case and type sensitive. See: [`union()`](#union), [`append()`](#append) ```js var foo = ['a', 'b'], bar = ['b', 'd']; combine(foo, bar); // ['a', 'b', 'd'] ``` ## compact(arr):Array Returns a new Array without any `null` or `undefined` values. Note that it will keep empty strings and other falsy values (simillar to Ruby Array#compact). ```js var arr = [0, 1, null, false, '', 'foo', undefined, 'bar']; compact(arr); // [0, 1, false, '', 'foo', 'bar']; ``` ## contains(arr, value):Boolean Checks if Array contains value. Alias to `indexOf(arr, val) !== -1`. ```js var arr = [1, 2, 3]; contains(arr, 2); // true contains(arr, 'foo'); // false ``` ## difference(...arrs):Array Return a new Array with elements that aren't present in the other Arrays besides the first one. Works like [Python set#difference](http://docs.python.org/library/stdtypes.html#set.difference). It will remove duplicates. See: [`xor()`](#xor), [`intersection()`](#intersection) ```js var a = ['a', 'b', 1]; var b = ['c', 1]; difference(a, b); // ['a', 'b'] ``` ## equals(a, b, [compare]):Boolean Checks if both arrays are equal. ```js equals([1, 2], [1, 2]); // true equals([2, 4], [1, 2]); // false ``` By default it uses the [lang/is](lang.html#is) as the `compare` function but you can pass a custom function to change the behavior. ```js function loose(a, b) { return a == b; } equals(['1', 2], [1, 2], loose); // true ``` See: [object/equals](object.html#equals), [lang/deepEquals](lang.html#deepEquals) ## every(arr, callback, [thisObj]):Array Crossbrowser `Array.every()`. Tests whether all elements in the array pass the test implemented by the provided function. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). ```js var items = [1, 'foo', 'bar']; every(items, isString); // false every(items, isFunction); // false every(items, function(val, key, arr){ return val != null; }); // true ``` more info at [MDN Array#every](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/every) It also supports a shorthand syntax: ```js var items = [{id:1, active:true}, {id:3, active:true}, {id:8, active:true}]; // all items with `id === 8` every(items, {id:8}); // false // `active` is truthy on all items every(items, 'active'); // true ``` ## filter(arr, callback, [thisObj]):Array Crossbrowser `Array.filter()`. Creates a new array with all elements that pass the callback test. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). ```js var nums = [1, 2, 3, 4, 5, 6]; var oddNumbers = filter(nums, function(val, key, arr){ return (val % 2) !== 0; }); // > [1, 3, 5] ``` more info at [MDN Array#filter](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/filter) Filter also supports shorthand notation: ```js var users = [ {name:'john', surname:'connor', beard:false}, {name:'john', surname:'doe', beard:true}, {name:'jane', surname:'doe', beard:false} ]; // filter item that matches all properties/values pairs filter(users, {name:'john', beard:false}); // > [{name:'john', surnname:'connor', beard:false}] // items where 'beard' is a truthy value filter(users, 'beard'); // > [{name:'john', surnname:'doe', beard:true}] ``` See [`reject()`](#reject) ## find(arr, callback, [thisObj]):* Loops through all the items in the Array and returns the first one that passes a truth test (callback). ```js var arr = [123, {a:'b'}, 'foo', 'bar']; find(arr, isString); // "foo" find(arr, isNumber); // 123 find(arr, isObject); // {a:'b'} ``` Find also supports shorthand notation: ```js var users = [ {name:'john', surname:'connor', beard:false}, {name:'john', surname:'doe', beard:true} ]; // first item that matches all properties/values pairs find(users, {name:'john'}); // {name:'john', surnname:'connor', beard:false} // first item where 'beard' is a truthy value find(users, 'beard'); // {name:'john', surnname:'doe', beard:true} ``` See: [findIndex()](#findIndex), [findLast()](#findLast), [findLastIndex()](#findLastIndex) ## findLast(arr, callback, [thisObj]):* Loops through all the items in the Array (starting from last item) and returns the first one that passes a truth test (callback). ```js var arr = [123, {a:'b'}, 'foo', 'bar']; findLast(arr, isString); // "bar" findLast(arr, isNumber); // 123 findLast(arr, isObject); // {a:'b'} ``` `findLast` also supports shorthand notation: ```js var users = [ {name:'john', surname:'connor', beard:false}, {name:'john', surname:'doe', beard:true} ]; // last item that matches all properties/values pairs findLast(users, {name:'john'}); // {name:'john', surnname:'doe', beard:true} // last item where 'beard' is a truthy value findLast(users, 'beard'); // {name:'john', surnname:'doe', beard:true} ``` See: [find()](#find), [findIndex()](#findIndex), [findLastIndex()](#findLastIndex) ## findIndex(arr, iterator, [thisObj]):Number Loops through the items in the Array and returns the index of the first one that passes a truth test (callback). Returns `-1` if no item was found that passes the truth test. ```js var arr = [1, { a: 1 }, 'foo', 'bar']; findIndex(arr, isString); // 2 findIndex(arr, isNumber); // 0 findIndex(arr, isObject); // 1 findIndex(arr, isRegExp); // -1 ``` `findIndex` also supports shorthand notation: ```js var pets = [ { pet: 'dog', name: 'Sam' }, { pet: 'dog', name: 'Maggie' } ]; findIndex(pets, { pet: 'dog' }); // 0 findIndex(pets, { name: 'Maggie' }); // 1 ``` See: [find()](#find), [findLastIndex()](#findLastIndex) ## findLastIndex(arr, iterator, [thisObj]):Number Loops through the items in the Array on the reverse order and returns the index of the first one that passes a truth test (callback). Returns `-1` if no item was found that passes the truth test. ```js var arr = [1, { a: 1 }, 'foo', 'bar']; findLastIndex(arr, isString); // 3 findLastIndex(arr, isNumber); // 0 findLastIndex(arr, isObject); // 1 findLastIndex(arr, isRegExp); // -1 ``` `findLastndex` also supports shorthand notation: ```js var pets = [ { pet: 'dog', name: 'Sam' }, { pet: 'dog', name: 'Maggie' } ]; findLastIndex(pets, { pet: 'dog' }); // 1 findLastIndex(pets, { name: 'Sam' }); // 0 ``` See: [find()](#find), [findIndex()](#findIndex) ## flatten(arr, [level]):Array Recursively flattens an array. A new array containing all the elements is returned. If `level` is specified, it will only flatten up to that level. Note that arrays within objects will not be flattened. ### Example ```js flatten([1, [2], [3, [4, 5]]]); // > [1, 2, 3, 4, 5] flatten([1, [2], [3, [4, 5]]], 1); // > [1, 2, 3, [4, 5]] ``` See: [`object/flatten()`](./object.html#flatten) ## forEach(arr, callback, [thisObj]):void Crossbrowser `Array.forEach()`. It allows exiting the iteration early by returning `false` on the callback. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). ```js var items = ['foo', 'bar', 'lorem', 'ipsum']; forEach(items, function(val, key, arr){ console.log(key +' : '+ val); if (val === 'lorem') { // stop iteration (break) return false; } }); ``` more info at [MDN Array#forEach](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/forEach) ## groupBy(arr, [categorize=identity], [thisObj]):Object Groups array elements by the `key` returned from the `categorize` function. It will use the [function/identity](function.html#identity) as the default `categorize` function. ```js var items = ['lorem', 'ipsum', 'foo', 'bar', 'baz']; groupBy(items, function(val) { return val.length }); // > {'3': ['foo', 'bar', 'baz'], '5': ['lorem', 'ipsum']} ``` ## indexOf(arr, item, [fromIndex]):Number Crossbrowser `Array.indexOf()`. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). more info at [MDN Array#indexOf](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/indexOf) ## indicesOf(arr, item, [fromIndex]):Number Returns an array of indices where `item` is found in the array. Like `array/indexOf` it does loop over sparse items in the array. The optional `fromIndex` parameter can limit the scope, the same way as it does in indexOf. ```js var items = ['lorem', 'ipsum', 'foo', 'ipsum', 'ipsum']; indicesOf(items, 'ipsum'); // > [1, 3, 4] indicesOf(items, 'ipsum', 1); // > [3, 4] ``` ## insert(arr, ...items):Number Push items into array only if they aren't contained by it. Returns the new `length` of the array. See: [`remove()`](#remove), [`removeAll()`](#removeAll), [`contains()`](#contains) ```js var arr = ['a', 'b']; insert(arr, 'a'); // 2 : ['a', 'b'] insert(arr, 'c'); // 3 : ['a', 'b', 'c'] insert(arr, 1, 2, 'b'); // 5 : ['a', 'b', 'c', 1, 2] ``` ## intersection(...arrs):Array Return a new Array with elements common to all Arrays. Similar to Python set#intersection and underscore.js intersection. It will remove duplicates. See: [`difference()`](#difference), [`xor()`](#xor) ```js var a = ['a', 'b', 1], b = ['c', 1], c = [1, 2, 3]; intersection(a, b, c); // [1] ``` ## invoke(arr, methodName[, ...args]):Array Call `methodName` on each item of the array passing custom arguments if needed. ```js invoke([[3,2,1], [9,5,2]], 'sort'); // [[1,2,3], [2,5,9]] ``` ## join(arr, [separator]):String Joins the strings in `arr`, inserting `separator` between each value. This ignores null values and empty strings that are in the array. `separator` defaults to an empty string. This will convert all non-string objects in the array to a string. ### Example ```js join(['a', 'b', 'c']); // 'abc' join(['foo', 'bar'], ', '); // 'foo, bar' join([null, 'foo', '', 'bar', undefined], ':'); // 'foo:bar' ``` ## last(arr):* Returns the last element of an array without modifying the array. ```js last( [1, 2, 3, 4] ) // > 4 last( ['foo', 'bar'] ) // > 'bar' ``` ## lastIndexOf(arr, item, [fromIndex]):Number Crossbrowser `Array.lastIndexOf()`. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). more info at [MDN Array#lastIndexOf](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/lastIndexOf) ## map(arr, callback, [thisObj]]):Array Crossbrowser `Array.map()`. Creates a new array with the results of calling a provided function on every element in this array. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). See: [`collect()`](#collect) ```js var nums = [1,2,3,4]; var double = map(nums, function(val, key, arr){ return val * 2; }); // > [2, 4, 6, 8] ``` more info at [MDN Array#map](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/map) It also supports a shorthand notation which can be used to achieve same result as [`array/pluck`](#pluck): ```js var src = ['lorem', 'ipsum', 'foo', 'amet']; // grab the "length" property of all items var lengths = map(src, 'length'); // [5, 5, 3, 4] ``` ## max(arr, [iterator], [thisObj]):* Returns maximum value inside array or use a custom iterator to define how items should be compared. See: [`min()`](#min) ```js max([10, 2, 7]); // 10 max(['foo', 'lorem', 'amet'], function(val){ return val.length; }); // 'lorem' ``` It also supports a shorthand notation: ```js max(['foo', 'lorem', 'amet'], 'length'); // "lorem" ``` ## min(arr, [iterator], [thisObj]):* Returns minimum value inside array or use a custom iterator to define how items should be compared. See: [`max()`](#max) ```js min([10, 2, 7]); // 2 min(['foo', 'lorem', 'amet'], function(val){ return val.length; }); // 'foo' ``` It also supports a shorthand notation: ```js min(['foo', 'lorem', 'amet'], 'length'); // "foo" ``` ## pick(arr, [nItems]):* Gets random item(s) and removes it from the original array. If `nItems` is specified it will return a new Array contained the *picked* items otherwise it returns a single item. See: [`random/choice()`](./random.html#choice) ### Example: ```js var arr = [1, 2, 3, 4, 5, 6]; var item1 = pick(arr); // 4 var item2 = pick(arr); // 1 var items = pick(arr, 2); // [5, 2] console.log(arr); // [3, 6] ``` ## pluck(arr, propName):Array Extract a list of property values. See: [`function/prop()`](function.html#prop) ```js var users = [{name : 'John', age: 21}, {name: 'Jane', age : 27}]; var names = pluck(users, 'name'); // ["John", "Jane"] var ages = pluck(users, 'age'); // [21, 27] ``` ## range([start], stop[, step]):Array Creates a new Array with all the values inside the range. Works similarly to Python#range or PHP#range. ### Arguments 1. `[start]` (Number) : Range start. Default is `0`. 2. `stop` (Number) : Range limit. 3. `[step]` (Number) : Step size. Default is `1`. ### Example ```js range(5); // [0, 1, 2, 3, 4, 5] range(0, 5); // [0, 1, 2, 3, 4, 5] range(0, 5, 2); // [0, 2, 4] range(20, 40, 5); // [20, 25, 30, 35, 40] ``` ## reduce(arr, fn):* Crossbrowser `Array.reduce()`. Apply a function against an accumulator and each value of the array (from left-to-right) as to reduce it to a single value. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). more info at [MDN Array#reduce](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/reduce) ## reduceRight(arr, fn):* Crossbrowser `Array.reduceRight()`. Apply a function simultaneously against two values of the array (from right-to-left) as to reduce it to a single value. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). more info at [MDN Array#reduceRight](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/reduceRight) ## reject(arr, fn, thisObj):Array Creates a new array with all the elements that do **not** pass the truth test. Opposite of [`filter()`](#filter). See [`filter()`](#filter) ### Example ```js var numbers = [1, 2, 3, 4, 5, 6]; reject(numbers, function(x) { return (x % 2) !== 0; }); // [2, 4, 6] ``` It also supports a shorthand syntax: ```js var users = [ {name:'john', surname:'connor', beard:false}, {name:'john', surname:'doe', beard:true}, {name:'jane', surname:'doe', beard:false} ]; // reject items that matches all properties/values pairs reject(arr, {name:'john'}); // > [{name:'jane', surnname:'doe', beard:false}] // reject items where 'beard' is a truthy value filter(arr, 'beard'); // > [{name:'john', surnname:'connor', beard:false}, // {name:'jane', surname:'doe', beard:false}] ``` ## remove(arr, item):void Remove a single item from the array. IMPORTANT: it won't remove duplicates, just a single item. ### Example ```js var foo = [1, 2, 3, 4]; remove(foo, 2); console.log(foo); // [1, 3, 4] ``` ## removeAll(arr, item):void Remove all instances of an item from the array. ### Example ```js var foo = [1, 2, 3, 4, 2, 2]; removeAll(foo, 2); console.log(foo); // [1, 3, 4]; ``` ## reverse(arr):void Returns a copy of the array with all elements in reversed order. ### Example ```js var foo = [1, 2, 3, 4, 5]; var bar = reverse(foo); console.log(bar); // [5, 4, 3, 2, 1]; console.log(foo); // [1, 2, 3, 4, 5]; ``` ## shuffle(arr):Array Returns a new Array with items randomly sorted (shuffled). Similar to Ruby Array#shuffle. ### Example ```js var arr = ['a', 'b', 'c', 'd', 'e']; shuffle(arr); // ['b', 'd', 'e', 'c', 'a'] ``` ## slice(arr, [start], [end]):Array Returns a new array containing the items from `arr` from the start index to the end index. If `start` is omitted, it will start at `0`. If `end` is omitted, it will used the last index of the array. If `start` or `end` is negative, it is used as an offset from the end of the array. It will also convert array-like objects to arrays. ### Example ```js slice([1, 2, 3, 4], 1, 2); // [2, 3] slice([1, 2, 3], 1); // [2, 3] slice([1, 2, 3]); // [1, 2, 3] slice({ length: 2, 0: 'a', 1: 'b' }); // ['a', 'b'] slice([1, 2, 3], 0, -1); // [1, 2] slice([1, 2, 3], -2); // [2, 3] ``` ## some(arr, callback, [thisObj]):Array Crossbrowser `Array.some()`. Tests whether some element in the array passes the test implemented by the provided function. It differs from ES5 since it will also loop over sparse items in the array to normalize the behavior across browsers (avoid inconsistencies). ```js var items = [1, 'foo', 'bar']; some(items, isString); // true some(items, isFunction); // false ``` more info at [MDN Array#some](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/some) It also supports a shorthand syntax: ```js var items = [{id:1, active:true}, {id:3, active:false}, {id:8, active:false}]; // at least one item with `id === 8` some(items, {id:8}); // true // `active` is truthy on at least one item some(items, 'active'); // true ``` see also: [`object/matches`](object.html#matches) ## sort(arr, [compareFn]):Array Returns a sorted Array using the [Merge Sort](http://en.wikipedia.org/wiki/Merge_sort) algorithm (stable sort). The `Array.prototype.sort` browser implementations differ since the sorting algorithm isn't described in the ES spec - [in V8 it isn't stable](http://code.google.com/p/v8/issues/detail?id=90) and [on Firefox it is stable](https://bugzilla.mozilla.org/show_bug.cgi?id=224128) - so this function doesn't use the browser native implementation and is recommended in cases where a stable sort is required (items should preserve same order if already sorted). **Important:** It does logical comparisson by default (greater/less than) and not a string comparisson like the native `Array#sort`. ### compareFn If `compareFn` is supplied elements are sorted based on the value returned by the `compareFn`. - If `compareFn(a, b)` is less than `0`, sort `a` to a lower index than `b`. - If `compareFn(a, b)` returns `0`, leave `a` and `b` unchanged with respect to each other, but sorted with respect to all different elements. - If `compareFn(a, b)` is greater than `0`, sort `b` to a lower index than `a`. See: [`sortBy`](#sortBy) ### Example ```js sort([187, 23, 47, 987, 12, 59, 0]); // [0, 12, 23, 47, 59, 187, 987] sort(['a', 'z', 'c', 'beta', 'b']); // ['a', 'b', 'beta', 'c', 'z'] // ['sit', 'amet', 'lorem', 'ipsum'] sort(['lorem', 'ipsum', 'sit', 'amet'], function(a, b){ // sort by length, items with same length // will keep the relative order (stable) return a.length - b.length; }); // [4, 3, 2, 1] sort([2, 3, 1, 4], function(a, b){ // reverse sort return b - a; }); ``` ## sortBy(arr, callback, [context]):Array Returns an array sorted by the result of the callback. The callback is called for each item that is to be sorted, and the results of the callback are used to sort the array. The callback is called with the item as the first parameter, optionally with the provided context. It also supports a shorthand notation which can be used to sort by a property name. See: [`sort`](#sort) ```js // Returns [{ a: 1 }, { a: 2 }, { a: 3 }] sortBy([{ a: 1 }, { a: 3 }, { a: 2 }], function(item) { return item.a; }); // Same as above, using shorthand notation sortBy([{ a: 1 }, { a: 3 }, { a: 2 }], 'a'); ``` ## split(arr, [segments]):Array Splits an array into a fixed number of segments. The number of segments is specified by `segments` and defaults to 2. If the array cannot be evenly split, the first segments will contain the extra items. If `arr` is empty, an empty array is returned. If `arr.length` is less than `segments`, then the resulting array will have `arr.length` number of single-element arrays. ### Example ```js split([1, 2, 3, 4, 5], 3) // [ [1, 2], [3, 4], [5] ] split([1, 2, 3, 4, 5]) // [ [1, 2, 3], [4, 5] ] split([]) // [] split([1, 2], 3) // [ [1], [2] ] ``` ## take(times, callback, [thisObj]):Array Builds a new array based on the returned values from the given `callback`. ```js take(4, function(i, total) { return i / total; }); // > [0, 0.25, 0.5, 0.75] ``` see: [function/times](../function.html#times) ## toLookup(arr, key):Object Create an object that indexes the items in the array by a key. If `key` is a function, the key for each value in the resulting object will be the result of calling the function with the value as an argument. Otherwise `key` specifies the property on each value to use as the key. ### Example ```js var foo = [{ name: 'a', thing: 1 }, { name: 'b', thing: 2 }]; // { a: { name: 'a', thing: 1 }, b: { name: 'b', thing: 2 } } toLookup(foo, 'name'); // same as above toLookup(foo, function (value) { return value.name; }); ``` ## union(...arrs):Array Concat multiple arrays removing duplicates. ```js var a = ['a', 'b'], b = ['c', 'a'], c = [1, 'b', 2, 3, 'a']; //note that unique remove from begin to end union(a, b, c); // ['c', 1, 'b', 2, 3, 'a'] ``` ## unique(arr, [compare]):Array Return a new Array of unique items. **IMPORTANT:** duplicates are removed starting from begining of array. ```js var arr = [1, 2, 3, 4, 2, 2, 4]; var foo = unique(arr); console.log(foo); // > [1, 3, 2, 4]; // you also have the option to set a custom compare function var users = [{name: 'john'}, {name: 'paul'}, {name: 'john'}]; var uniqueNames = unique(arr, function(a, b){ return a.name === b.name; }); console.log(uniqueNames); // > [{name: 'paul'}, {name: 'john'}] ``` ## xor(arr1, arr2):Array Exclusive OR. Returns items that are present in a single array. Works like [Python set#symmetric_difference](http://docs.python.org/library/stdtypes.html#set.symmetric_difference) renamed for brevity. It will remove duplicates. See: [`difference()`](#difference), [`intersection()`](#intersection) ```js var a = ['a', 'b', 1]; var b = ['c', 1]; xor(a, b); // ['a', 'b', 'c'] ``` ## zip(...arrs):Array Groups the elements of each array at their corresponding indexes. Useful for separate data sources that are coordinated through matching array indexes. For a matrix of nested arrays, `zip.apply(...)` can transpose the matrix in a similar fashion. ```js // [['moe', 30, true], ['larry', 40, false], ['curly', 50, false]] zip(['moe', 'larry', 'curly'], [30, 40, 50], [true, false, false]); ``` ------------------------------------------------------------------------------- For more usage examples check specs inside `/tests` folder. Unit tests are the best documentation you can get...