Null Vs. Undefined in JavaScript

In JavaScript, both null and undefined represent the absence of a value. However, they have distinct use cases and behaviors. Let's delve into the details with examples:

Undefined in JacaScript

  1. undefined is a primitive value that indicates a variable has been declared but not assigned any value.
  2. It's the default value for uninitialized variables and function parameters.
  3. When accessing an object property or array element that doesn't exist, it results in undefined.
var x; console.log(x); // Output: undefined function exampleFunc(y) { console.log(y); // Output: undefined } exampleFunc(); var obj = { key: "value" }; console.log(obj.nonExistent); // Output: undefined

Null in JacaScript

  1. null is an assignment value that represents the intentional absence of any object value.
  2. It's often used to indicate that a variable should have no value or to reset a variable.
  3. Unlike undefined, null is explicitly assigned.
var z = null; console.log(z); // Output: null var user = null; console.log(user); // Output: null var arr = [1, 2, 3]; arr = null; console.log(arr); // Output: null

Comparing Undefined and Null

What's the difference between Null and Undefined Javascript
console.log(undefined == null); // Output: true console.log(undefined === null); // Output: false


JacaScript undefined indicates the lack of an assigned value or the non-existence of a property, while null signifies an intentional absence of value. Understanding the distinction between these two concepts is crucial for writing effective and reliable JavaScript code.