Array.prototype.some()

The some() method tests whether at least one element in the array passes the test implemented by the provided function. It returns true if, in the array, it finds an element for which the provided function returns true; otherwise it returns false. It doesn't modify the array.

Syntax

// Arrow function
some((element) => { /* ... */ } )
some((element, index) => { /* ... */ } )
some((element, index, array) => { /* ... */ } )

// Callback function
some(callbackFn)
some(callbackFn, thisArg)

// Inline callback function
some(function(element) { /* ... */ })
some(function(element, index) { /* ... */ })
some(function(element, index, array){ /* ... */ })
some(function(element, index, array) { /* ... */ }, thisArg)

Parameters

callbackFn

A function to test for each element.

The function is called with the following arguments:

element

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.

thisArgOptional

A value to use as this when executing callbackFn.

Return value

true if the callback function returns a truthy value for at least one element in the array. Otherwise, false.

Description

The some() method executes the callbackFn function once for each element present in the array until it finds the one where callbackFn 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. callbackFn is invoked only for indexes of the array with assigned values. It is not invoked for indexes which have been deleted or which have never been assigned values.

callbackFn 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 used as the callback's this value. Otherwise, the value undefined will be used as its this value. The this value ultimately observable by callbackFn 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 callbackFn. Elements which are assigned to indexes already visited, or to indexes outside the range, will not be visited by callbackFn. If an existing, unvisited element of the array is changed by callbackFn, its value passed to the visiting callbackFn will be the value at the time that some() visits that element's index. Elements that are deleted are not visited.

Warning: Concurrent modification of the kind described in the previous paragraph frequently leads to hard-to-understand code and is generally to be avoided (except in special cases).

Note: Calling this method on an empty array returns false for any condition!

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(x => x > 10);  // false
[12, 5, 8, 1, 4].some(x => x > 10); // true

Checking whether a value exists in an array

To mimic the function of the includes() method, this custom function returns true if the element exists in the array: 

const 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

const 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

const TRUTHY_VALUES = [true, 'true', 1];

function getBoolean(value) {
  'use strict';

  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

Specifications

Specification
ECMAScript Language Specification
# sec-array.prototype.some

Browser compatibility

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See also