JavaScript for Developers 14 - Difference between undefined and null

A commonly asked question is how to differentiate between undefined and null. When to use what? We'll cover this difference in this tutorial.

[danialmalik]

NULL is Explicitly Defined, Undefined is Implicitly Defined

[viplovedev]

Sir, the segment where you talk about the difference between undefined and null, you just taught not just us Javascript but common sense itself. Thank you.

[aldin]

I got into coding not long ago and found your channel just recently. Had to stop the video to express my sincerest gratitude! Wow, just WOW! THANK YOU!

[shashikumar-qwez]

The explanation you are giving abt the topics are just mind blowing. kindly please give more to us like this. respect for this videos hats off to u.

[markcaruso]

What a terrific analogy for the difference between undefined and null - Thanks so much

[lpjznsm]

Kaushik, I am sure you must have brainstormed this for a while, to make us understand in a go! Superb analogy. Keep it up!

[dreamscapeai]

Best analogy I've seen, hats off to you

[saptaswasarkar]

Putting things so simple, and knitted so well. Thanks for such great learning session. Salute.

[MrTORISSIMO]

I like the metaphor with form example that's exactly what I needed. Thanks

[prabhupadswain]

Hello Sir, do you have videos on Java tutorials also.(J2SE, J2EE)? I mainly came here for Java tutorials getting refered from someone on Quora. But, I found JavaScript Series videos which are absolutely great till now. Please, let me know if you have tutorials on Core Java and Jdbc etc

[nitintakale]

is it like this ???

you declare a variable in javascript like this-
var a;

now, since javascript is a type-less language. We don't declare a type while declaring a variable. And the type of a variable depends on the type of value assigned to it. At runtime this can change.

So when we declare a variable saying var a; but we don't initialize it, since there is no type assigned to the variable javaScript initializes it with undefined. (instead of initializing it with say - 0.0, "", or false)

Further Any value in JavaScript that is not a string, a number, true, false, null, or undefined is an object.

if a variable is null it means absence of Object in javaScript.

you can declare a variable say
var obj = null;
and

var num;

here obj is going to be null & num is going to be undefined.
if we check the type of these 2


console.log(typeof num); // this will print undefined

console.log(typeof obj); // this will print Object - it means null is absence of object....

[dhananjaypatankar]

That's a good one...I have a middle name .. ;)

[muhammedismail]

I agree your video give a great explanation but some points you mix java and javascript so who know java prog. then them for it to difficult to understand.
So I suggest dont use simply java u used with full name as javascript.... I hope u got it...

[javasoldier]

no sense from dev prospective - null and undefined = no value;

[onxx-]

im not racist but im sorry if this comes off a bit racist but, why tf is every coding video explained by an indian makes it so much harder to understand let alone understanding the concepts of coding pisses me off