Null vs. Undefined in JavaScript: What\'s the Difference and How to Check for Them?

Diving into Null and Undefined in JavaScript

JavaScript's handling of null and undefined can often lead to confusion. Let's unravel the mysteries behind these two concepts.

Why is null an Object?

Despite having primitive values, null is classified as an object in JavaScript. This unconventional behavior stems from JavaScript's historical implementation, where objects were used as a catch-all for non-primitive values.

Checking for null and undefined

To check for the existence of either null or undefined, it's recommended to use the strict equality operator (===) instead of the loose equality operator (==). This is because the loose equality operator coerces values and may result in unexpected outcomes:

if (object == null) // Not recommended
if (!object) // Recommended

Understanding the Difference between null and undefined

• undefined: Represents a variable that has not been assigned a value or a property that doesn't exist. It's a primitive type with no type information.
• null: Denotes an intentionally empty or unknown value. It's an object with a type of "null" and acts as a placeholder when a value is expected but not available.

Consider the following example:

let name; // undefined
let object = null; // null

When accessing name, JavaScript reports it as undefined, indicating it doesn't recognize the variable. Conversely, object is recognized and returns null, specifying that it's an empty or unknown value.

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