What is the difference between null and undefined in JavaScript?

Question

I want to know what the difference is between null and undefined in JavaScript.

Answer 1

The difference between undefined and null is minimal, but there is a difference. A variable whose value is undefined has never been initialized. A variable whose value is null was explicitly given a value of null, which means that the variable was explicitly set to have no value. If you compare undefined and null by using the null==undefined expression, they will be equal.