Array.prototype.some()
The some()
method tests whether some element in the array passes the test implemented by the provided function.
Syntax
<var>arr</var>.some(<var>callback</var>[, <var>thisArg</var>])
Parameters
callback
- Function to test for each element, taking three arguments:
currentValue
- The current element being processed in the array.
index
- The index of the current element being processed in the array.
array
- The array
some()
was called upon.
thisArg
- Optional. Value to use as
this
when executingcallback
.
Return value
true
if the callback function returns a truthy value for any array element; otherwise, false
.
Description
some()
executes the callback
function once for each element present in the array until it finds one where callback
returns a truthy value (a value that becomes true when converted to a Boolean). If such an element is found, some()
immediately returns true
. Otherwise, some()
returns false
. callback
is invoked only for indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.
callback
is invoked with three arguments: the value of the element, the index of the element, and the array object being traversed.
If a thisArg
parameter is provided to some()
, it will be passed to callback
when invoked, for use as its this
value. Otherwise, the value undefined
will be passed for use as its this
value. The this
value ultimately observable by callback
is determined according to the usual rules for determining the this
seen by a function.
some()
does not mutate the array on which it is called.
The range of elements processed by some()
is set before the first invocation of callback
. Elements that are appended to the array after the call to some()
begins will not be visited by callback
. If an existing, unvisited element of the array is changed by callback
, its value passed to the visiting callback
will be the value at the time that some()
visits that element's index; elements that are deleted are not visited.
Examples
Testing value of array elements
The following example tests whether any element in the array is bigger than 10.
function isBiggerThan10(element, index, array) { return element > 10; } [2, 5, 8, 1, 4].some(isBiggerThan10); // false [12, 5, 8, 1, 4].some(isBiggerThan10); // true
Testing array elements using arrow functions
Arrow functions provide a shorter syntax for the same test.
[2, 5, 8, 1, 4].some(elem => elem > 10); // false [12, 5, 8, 1, 4].some(elem => elem > 10); // true
Checking whether a value exists in an array
The following example returns true
if the element exists in the array:
var fruits = ['apple', 'banana', 'mango', 'guava']; function checkAvailability(arr, val) { return arr.some(function(arrVal) { return val === arrVal; }); } checkAvailability(fruits, 'kela'); //false checkAvailability(fruits, 'banana'); //true
Checking whether a value exists using an arrow function
var fruits = ['apple', 'banana', 'mango', 'guava']; function checkAvailability(arr, val) { return arr.some(arrVal => val === arrVal); } checkAvailability(fruits, 'kela'); //false checkAvailability(fruits, 'banana'); //true
Converting any value to Boolean
var TRUTHY_VALUES = [true, 'true', 1]; function getBoolean(a) { 'use strict'; var value = a; if (typeof value === 'string') { value = value.toLowerCase().trim(); } return TRUTHY_VALUES.some(function(t) { return t === value; }); } getBoolean(false); // false getBoolean('false'); // false getBoolean(1); // true getBoolean('true'); // true
Polyfill
some()
was added to the ECMA-262 standard in the 5th edition; as such it may not be present in all implementations of the standard. You can work around this by inserting the following code at the beginning of your scripts, allowing use of some()
in implementations which do not natively support it. This algorithm is exactly the one specified in ECMA-262, 5th edition, assuming Object
and TypeError
have their original values and that fun.call
evaluates to the original value of Function.prototype.call()
.
// Production steps of ECMA-262, Edition 5, 15.4.4.17 // Reference: http://es5.github.io/#x15.4.4.17 if (!Array.prototype.some) { Array.prototype.some = function(fun/*, thisArg*/) { 'use strict'; if (this == null) { throw new TypeError('Array.prototype.some called on null or undefined'); } if (typeof fun !== 'function') { throw new TypeError(); } var t = Object(this); var len = t.length >>> 0; var thisArg = arguments.length >= 2 ? arguments[1] : void 0; for (var i = 0; i < len; i++) { if (i in t && fun.call(thisArg, t[i], i, t)) { return true; } } return false; }; }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 5.1 (ECMA-262) The definition of 'Array.prototype.some' in that specification. |
Standard | Initial definition. Implemented in JavaScript 1.6. |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Array.prototype.some' in that specification. |
Standard | |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Array.prototype.some' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | (Yes) | 1.5 (1.8) | 9 | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | 1.0 (1.8) | (Yes) | (Yes) | (Yes) |
See also
Array.prototype.find()
Array.prototype.forEach()
Array.prototype.every()
TypedArray.prototype.some()
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/javascript/reference/global_objects/array/some