JavaScript Syntax

Statements

A JavaScript program is a list of statements, run from top to bottom. Statements usually end with a semicolon ;.

let x = 5;
let y = 6;
let z = x + y;
console.log(z);

11

Semicolons are mostly optional — JavaScript inserts them automatically at line ends — but most style guides use them to avoid surprises.

Code blocks

Curly braces { } group statements into a block, for example the body of an if or a function. Indentation is only for humans — but always indent consistently (2 spaces is the most common style in JavaScript).

let temperature = 31;
if (temperature > 30) {
  console.log("It's hot");
  console.log("Drink water");
}
console.log("Done");

It's hot
Drink water
Done

Case sensitivity and identifiers

JavaScript is case-sensitive: total, Total and TOTAL are different names. Names (identifiers) may contain letters, digits, _ and $, but cannot start with a digit. The convention is camelCase: firstName, totalPrice, isLoggedIn.