Array.prototype.some()

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, 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 executing callback.

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: https://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

Browser compatibility

See also

• Array.prototype.find()
• Array.prototype.forEach()
• Array.prototype.every()
• TypedArray.prototype.some()