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

Per Ryan Morr's thorough article on this subject...

"Generally, if you need to assign a non-value to a variable or property, pass it to a function, or return it from a function, null is almost always the best option. To put it simply, JavaScript uses undefined and programmers should use null."

See Exploring the Eternal Abyss of Null and Undefined