23. Type Checking with typeof

The typeof operator is used to determine the data type of a variable or value. It returns a string representing the type.

Basic Usage

javascript let count = 5; let name = 'Dev'; let isReady = true; let data = null; let big = 1n;

console.log(typeof count); // Output: 'number' console.log(typeof name); // Output: 'string' console.log(typeof isReady); // Output: 'boolean' console.log(typeof undefined); // Output: 'undefined' console.log(typeof big); // Output: 'bigint'

// Functions are also considered objects in JS function greet() {}; console.log(typeof greet); // Output: 'function'

The null Anomaly Revisited

Remember the famous type error:

javascript console.log(typeof null); // Output: 'object' (A bug, but necessary to remember)

Checking for Objects (Excluding Null)

To safely check if something is a non-null object, you must combine checks:

javascript let myObj = { key: 'value' };

if (typeof myObj === 'object' && myObj !== null) { console.log('It is a valid object!'); }