JS Syntax

JavaScript syntax defines the rules for writing valid programs. The three core building blocks are literals (fixed values), variables (named storage), and expressions (computed values).

Try It — Syntax Building Blocks

Syntax Quick Reference

Concept	Example
Number literal	42, 3.14
String literal	"Hello", 'World'
Boolean literal	true, false
let variable	let name = "Alice";
const constant	const PI = 3.14;
Expression	width * height
Comment	// this is a comment

Tip: Use const for values that won’t change (most things). Use let when the value will be reassigned. Avoid var in modern JavaScript.