Data Types and Operators

Every value in JavaScript has a type, and the type determines what you can do with it.

let age = 16;               // number
let price = 19.99;          // also a number, JS doesn't separate int/float
let title = "Space Quest";  // string
let isAvailable = true;     // boolean

console.log(age + 4);       // 20
console.log(title.length);  // 10
console.log(isAvailable);   // true

Common types

Operators

• Arithmetic: + - * / work on numbers as you'd expect. + on two strings joins them instead of adding.
• Comparison: === checks if two values are equal (strictly, without converting types), !== checks if they're not equal, <, >, <=, >= compare numbers.

console.log(5 === 5);     // true
console.log(5 === "5");   // false, different types
console.log(10 > 3);      // true

Why === and not ==

JavaScript also has ==, which converts types before comparing ("5" == 5 is true), that hidden conversion causes subtle bugs. Prefer ===/!==, which compare exactly what you wrote.