JavaScript One-Liners Cheat Sheet

Flatten an Array

const flatten = arr => arr.flat(Infinity);
// or (older browsers)
const flatten = arr => [].concat(...arr);

Get Unique Values from an Array

const unique = arr => [...new Set(arr)];

Check if Object is Empty

const isEmpty = obj => Object.keys(obj).length === 0;

Swap Two Variables

[a, b] = [b, a];

Get Query Params from URL

const getQueryParams = url => 
  Object.fromEntries(new URLSearchParams(url.split('?')[1]));

Wait for X Milliseconds (Sleep)

const sleep = ms => new Promise(res => setTimeout(res, ms));