The Developer's Main Tools

Modern JS is 50% working with these methods.

1. forEach (Simple iteration)

["Bilbo", "Gandalf"].forEach(alert);

2. map (Creating a new array)

Applies a function to each element and returns an array of results.

let entryLen = ["Bilbo", "Gandalf"].map(item => item.length);
// [5, 7]

3. filter (Data cleansing)

Returns an array of elements that passed the test.

let users = [{id: 1, admin: true}, {id: 2, admin: false}];
let admins = users.filter(user => user.admin);