What are the differences between JavaScript's null and undefined?

Antek N

In JavaScript,null andundefined are two distinct values that represent the absence of a value. Although they are often used interchangeably, there are subtle differences between them: 1. Definition and Assignment: -undefined: -undefined is a primitive value that is automatically assigned to variables that have been declared but not initialized or assigned a value. - It also represents the default value of function parameters that are not provided. - It indicates the absence of any value or lack of definition. -null: -null is also a primitive value, but it is explicitly assigned to indicate the intentional absence of any object value. - It is typically used to represent the absence of an object or the deliberate assignment of no value. 2. Type and Value: -undefined: -undefined is a type in JavaScript that has only one value, which isundefined. - It is considered a falsy value, meaning it evaluates tofalse in a boolean context. -null: -null is a special object type in JavaScript that has only one value, which isnull. - It is also considered a falsy value. 3. Usage: -undefined: -undefined is commonly used to indicate the absence of a value or when a variable has not been assigned a value. - It can be problematic when accessing properties or methods of an undefined variable, as it can lead to errors. -null: -null is often used to explicitly indicate that a variable or property intentionally has no value or that an object is empty. - It can be used to reset the value of a variable or property to nothing. 4. Behavior in Comparisons: -undefined: - When using loose equality (==) or strict equality (===) operators,undefined is only equal tonull orundefined itself. - It is not equal to any other value, includingfalse,0, or an empty string. -null: - Similar toundefined,null is only equal tonull orundefined using the equality operators. - It is not equal to any other value. 5. Assignment and Mutation: -undefined: -undefined is automatically assigned to variables that have not been assigned any value. - It cannot be explicitly assigned or modified. -null: -null must be explicitly assigned to a variable or property to indicate the absence of a value. - It can be explicitly assigned or modified. Understanding the differences betweennull andundefined is important when handling variables, function returns, and object properties in JavaScript. While both represent the absence of a value,undefined is typically used to indicate the absence of assignment or definition, whilenull is used to indicate intentional absence or emptiness.