Variables & Data Types

Variables

let, const, var

Primitive types

const name = "Kofi";    // string\nconst age = 25;          // number\nconst price = 19.99;     // number (float)\nconst online = true;     // boolean\nconst nothing = null;    // null\nlet later;               // undefined

Checking types

typeof "hello";   // "string"\ntypeof 42;        // "number"\ntypeof true;      // "boolean"

Naming rules

• Use camelCase: firstName, not first_name
• Start with a letter, _ or $
• No spaces or reserved words
• Names should describe their meaning

Template literals

const greeting = `Hello, ${name}! You are ${age}.`;

Tip: Use const by default and only switch to let when you must reassign. This prevents accidental bugs.