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Converting an iterable to an array in JavaScript?

alexeychang profile image Alexey Chang ・1 min read

JavaScript ES6 introduced, among many other things, the spread operator (...)[https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax], which allows an iterable to be expanded in places where zero or more arguments or elements are expected.

We can use the spread operator to convert iterables or, as they are sometimes referred to, array-likes. Let's take a look at some examples:

String

When the spread operator is applied to a string, the result is an array of strings each one representing a character of the original string:

const name = 'Zelda';
const letters = [...name]; // 'Z', 'e', 'l', 'd', 'a'

Set

A Set is a collection of unique values. When the spread operator is applied to it, the result is an array of the stored values:

const data = [1, 2, 3, 1, 2, 4]
const values = new Set(data);
const uniqueValues = [...values]; // [1, 2, 3, 4]

Note that the above example is the basis for the uniqueElements snippet[https://www.30secondsofcode.org/js/s/unique-elements].

NodeList

A NodeList is a collection of nodes, returned by methods such as document.childNodes() or document.querySelectorAll(). While it implements some methods that help manipulate it as an array (e.g. NodeList.prototype.forEach()), it's oftentimes desirable to convert it to an array. When the spread operator is applied to it, the result is an array of the contained nodes:

const nodes = document.childNodes;
const nodeArray = [...nodes]; // [ <!DOCTYPE html>, html ]

Note that the above example is the basis for the nodeListToArray snippet[https://www.30secondsofcode.org/blog/s/js/s/node-list-to-array].

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