Data Types

(number, string, boolean, null, undefined, symbol)

Definition

A data type tells JavaScript what kind of information a value is.

Why Data Types Matter

Beach Ball Example

A beach ball won’t fit in a shoebox. Some actions only work with certain data types.

Math Class Example

If you want to solve: A + B = C, then A and B should be numbers. let A = 1; let B = “NIKE”;

This doesn’t work like normal math because “NIKE” is text, not a number.

The 6 Main Data Types

1. Number: Used for numbers (including decimals) let score = 100; let temperature = 98.6;

2. String: Text in quotes let name = “Andy”; let message = “Welcome to JavaScript!”;

3. Boolean: Only true or false let isGameOver = false; let isLoggedIn = true;

4. Null: Intentionally empty let currentPlayer = null;

5. Undefined: Not assigned yet let result; console.log(result); // undefined

6. Symbol (Advanced): A unique identifier let id = Symbol(“unique”);

Mini-Quiz

1. What data type is “Hello”?
2. What’s the difference between null and undefined?