# Well-known symbols in JavaScript

There are special built-in symbols that are used by JavaScript for service purposes. Such symbols are called well-known symbols.

An example of such a symbol is `Symbol.iterator`, which contains a function that iterates over arrays. Let's check its presence in some array:

`let arr = [1, 2, 3]; let func = arr[Symbol.iterator]; console.log(func);`

Make a `Map` collection. Check if it has the `Symbol.iterator` key.

Make a `Set` collection. Check if it has the `Symbol.iterator` key.

← →
↑
en ru