How does declaring variables like "const { x, y } = function()" work?

Question

JavaScript

I found here such declaration of variables

const { check, validationResult } = require('express-validator/check');

How it works and how it differs from the usualvar x = something

Answer 1

It differs in that more than one variable is returned, an object with named fields that expand into variables. It works something like this:

const {a, b} = {a:'foo', b:'bar'}
console.log(a) // -> foo
console.log(b) // -> bar

This is called destructuring .

Answer 2

This is destructuring. This is the same as

var obj = {a: 10, b: 15};
var a = obj.a;
var b = obj.b