Variables & Data Types

A variable is a named container for a value:

let score = 0; // can be reassigned const siteName = 'Aicloud'; // can't be reassigned var old = true; // the pre-2015 way — avoid

Rule of thumb: use const by default, let when the value must change, and never var.

Names can contain letters, digits, _ and $, can't start with a digit, and are case-sensitive (score and Score are different). The convention is camelCase: totalPrice.