When null should be used in javascript instead of undefined?

Question

What are the use cases of null in java-script?When null Should be used instead of undefined?

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/null — Pranav C Balan, May 15 '16 at 08:54
A duplicate of http://stackoverflow.com/questions/5076944/what-is-the-difference-between-null-and-undefined-in-javascript — ivan_pozdeev, May 15 '16 at 09:48

score 5 · Answer 1 · answered May 15 '16 at 08:54

This is a really broad question. You can/should use null whenever you want something that looks like an object reference but has no value. null is the object-reference-type version of undefined (or undefinedis the non-object-reference-type version of null).

There are a couple of places you may have to use null rather than undefined or something else: When dealing with host-provided objects that expect an object reference. Say we have a host-provided object foo that has a property thingy that may have a reference to another host-provided object. Because the host environment isn't required to make its objects full JavaScript objects, you may find that you get an error assigning a non-object-reference-type value like undefined to foo.thingy where assigning null to it works. (That said, most host environments will apply type coercion in that situation, and a large number of them now provide true JavaScript objects rather than fake ones.)

When null should be used in javascript instead of undefined?

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