JavaScript Cheat Sheet: Full Guide

Variables

var x = 1;   // function-scoped
let y = 2;   // block-scoped
const z = 3; // block-scoped, constant

Data Types

String, Number, Boolean, Undefined, Null, BigInt, Symbol, Object, Array, Function

Functions

function greet(name) { return "Hi " + name; }
const greet2 = (name) => "Hi " + name;

Arrays & Objects

let arr = [1, 2, 3];
arr.map(x => x * 2);
arr.filter(x => x > 1);

let obj = { name: "Alice", age: 25 };
console.log(obj.name);

Control Flow

if (x > 0) { }
for (let i = 0; i < 5; i++) { }
switch (x) { case 1: break; default: break; }

Async

async function getData() {
    let res = await fetch(url);
    let data = await res.json();
    return data;
}

Keep this cheat sheet handy as a quick reference while practicing JavaScript fundamentals.