Video: What is null and undefined in JavaScript?

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In this video you will learn about null and undefined in JavaScript. This video will explain similarity and differences between null and undefined

Published by

Dhananjay Kumar

Dhananjay Kumar is Developer Evangelist for Infragistics. He is a 8 times Microsoft MVP and well respected Developer Advocate in India.He is the author of 900+ Blog Posts, and can often be found speaking around India at conferences and hosting free workshops for programmers across the country. So far, he has hosted 60 free workshops on various topics like JavaScript, Angular, WCF, ASP.NET MVC, C#, Azure etc. Follow him on twitter @debug_mode for all the updates about his blog posts and workshops. You can send him email at debugmode [at] outlook [dot] com

5 thoughts on “Video: What is null and undefined in JavaScript?”

  1. Don’t provide this kind of information buddy check the following :

    1. null is not an object, it is a primitive value. You cannot add properties to it. We wrongly assume that it is an object, because typeof null returns “object”. But that is actually a bug in language itself(check this :

    2. Primitive value is a member of one of the following built-in types: Undefined, Null, Boolean, Number, and String; (this statemnt is directly from ECMA-262 (ECMAScript Language Specification))

    3. null is actually used to represent the absence of a value not “undefined”, but Javascript assigns undfined to any variable that is not initialized.

    4. Basically null value means a variable has been explicitly set as (no value = null) or has been initialized and defined to be nothing. While undefined means, it was probably never initialized or if it was it was never defined.

    5. Never ever use the == operator to check the equality in Javascript which actually perform type correcion before comparing the variables so obviously you will wrong results (use only ==== which will compare both the values & type – check ECMA-262 specs).

  2. I don’t agree with your points. I used == to demo that they represent almost same value. and yes null is an object

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