Array.prototype.includes()

Summary

The includes() method determines whether an array includes a certain element, returning true or false as appropriate.

Syntax

array.includes(searchElement[, fromIndex])

Parameters

searchElement

The element to search for.

fromIndex

Optional. The position in this array at which to begin searching for searchElement; defaults to 0.

Examples

[1, 2, 3].includes(2);     // true
[1, 2, 3].includes(4);     // false
[1, 2, 3].includes(3, 3);  // false
[1, 2, 3].includes(3, -1); // true
[1, 2, NaN].includes(NaN); // true

Polyfill

if (![].includes) {
  Array.prototype.includes = function(searchElement /*, fromIndex*/ ) {'use strict';
    var O = Object(this);
    var len = parseInt(O.length) || 0;
    if (len === 0) {
      return false;
    }
    var n = parseInt(arguments[1]) || 0;
    var k;
    if (n >= 0) {
      k = n;
    } else {
      k = len + n;
      if (k < 0) {k = 0;}
    }
    var currentElement;
    while (k < len) {
      currentElement = O[k];
      if (searchElement === currentElement ||
         (searchElement !== searchElement && currentElement !== currentElement)) {
        return true;
      }
      k++;
    }
    return false;
  };
}

Specifications

ES7 proposal: https://github.com/tc39/Array.prototype.includes.

Browser compatibility

See also

• TypedArray.prototype.includes()
• String.prototype.includes()
• Array.prototype.indexOf()