Lecture 127:- Null vs Undefined

In JavaScript, null and undefined are both used to represent the absence of a value, but they are used in different contexts.

undefined is a primitive value that is automatically assigned to variables that have been declared but not initialized, or to function arguments for which no value has been passed. For example:

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let x; console.log(x); // undefined function myFunction(y) {  console.log(y); } myFunction(); // undefined

null, on the other hand, is an explicit assignment of a non-value. It represents a deliberate non-value that a programmer has assigned to a variable, property, or object. For example:

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let x = null; console.log(x); // null let person = {  firstName: "John",  lastName: "Doe",  age: null }; console.log(person.age); // null

In summary, undefined is used when a variable has not been assigned a value, whereas null is used when a value intentionally does not exist.