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some

Summary

The some() method tests whether some element in the array passes the test implemented by the provided function.

Syntax

arr.some(callback[, thisArg])

Parameters

callback
Function to test for each element.
thisArg
Value to use as this when executing callback.

Description

some executes the callback function once for each element present in the array until it finds one where callback returns a true value. 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

Example: Testing value of array elements

The following example tests whether some element in the array is bigger than 10.

function isBigEnough(element, index, array) {
  return (element >= 10);
}
var passed = [2, 5, 8, 1, 4].some(isBigEnough);
// passed is false
passed = [12, 5, 8, 1, 4].some(isBigEnough);
// passed is 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.

if (!Array.prototype.some)
{
  Array.prototype.some = function(fun /*, thisArg */)
  {
    'use strict';

    if (this === void 0 || this === null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun !== 'function')
      throw new TypeError();

    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 Language Specification 5.1th Edition (ECMA-262) Standard Initial definition.
Implemented in JavaScript 1.6
ECMAScript Language Specification 6th Edition (ECMA-262) 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

Document Tags and Contributors

Contributors to this page: Sevenspade
Last updated by: Sevenspade,
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