JavaScript - change values in array during foreach

In this article, we would like to show you how to change values in array during foreach in JavaScript.

Quick solution (ES6):

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const letters = ['a', 'b', 'c'];

​

letters.forEach((element, index, array) => array[index] = 'x');

​

console.log(letters); // [ 'x', 'x', 'x' ]

In this example, we alternatively use forEach() with a second argument (context), which will be used as the value of this in each call to the callback function.

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var letters = ['a', 'b', 'c'];

​

letters.forEach(function(element, index) {

    this[index] = 'x';

}, letters);

​

console.log(letters); // [ 'x', 'x', 'x' ]

Warning:

This solution won't work with arrow functions.

1. Array.prototype.forEach() - JavaScript | MDN