How to Filter an Array in JavaScript

All JavaScript arrays have a built-in function .filter that allows you to filter certain elements and return a new array.

To filter a JavaScript array, you need to write a function that will determine the filtering rule.

Let’s imagine we have an array of strings:

const arr = ['pine', 'apple', 'pineapple', 'ball', 'roll'];

And we want to filter all string that are longer than 5 characters.

We call arr.filter and pass in an anonymous arrow funtion as an argument. This function will be called for every element of the array arr.

If it returns true, the element of the array will be included in the result. If false — it will be left out.

const longWords = arr.filter(item => item.length > 5);

console.log(longWords);   // ['pineapple']