JavaScript - Reference vs Primitive Values/ Types

One of the most common error sources: Not understanding what the difference between reference and primitive values is. This video will clear up the confusion.

Need more JavaScript Training?

Want to become a frontend developer? Consider diving into some of my courses:

See you in the videos!

[nuttaphonr.]

Thanks for concepts about reference vs primitives type and heap/stack too!
3:39 string is primitive (copy by value)
6:47 object, array are references type
7:05 primitives are store on stack
7:35 references are store on heap (take longer to access, store bigger amount of data)
8:40 stack (store like stack 'push on top')
9:16 heap (store pointer)
10:48 it assign a pointer not value
14:50 Object.assign create new object and merge with existing one
16:07 Object.assign doesn't deep clone
17:26 may use Lodash to clone instead
19:04 copy array

[josiahtobas]

Yeah man, you did a great job at explaining this stuff, I thought I understood it before but now I really understand it. God bless you 100 man. Peace.

[akshhatsrivastava]

That stack and heap explanation was very insightful. Thank you!

[naythaniel]

The short version, not 20 minute version of this, is that primitives (things that aren't containers for multiple separate values) make copies when passed to a function; while objects (containers for multiple separate values) make *references* to the object when passed to a function. In other words, when something is likely to be relatively small, it's okay to make a copy, but when it can potentially be enormously large, you just say where the thing is. Remember, primitives = copies && objects = references (which means addresses || pointers).

[spaces]

Max, you're very good at explaining complex topics in a simple way that makes them easier to understand. Thanks for the video.

[samirergaibi]

Thank you for this visual explanation, really made me understand. The pictures of the Stack and Heap sure helped as well ! :)

[energan]

Max, I don't know how you make explaining this so simple. If I would try to transfer what I have learned, I would confuse the hell out of the people listening. Thanks a lot for all the content you provide and for making many complicated subjects look actually, again, simple.

[dines]

This is one of the most confusing tutorial i've ever watched.
And I have to watch it again.
And again.
But thank you very much. Well done.

[jimmysignature]

This is excellent, the addition of the stack and heap explanations really clear this topic up. One of those things that is both easier and harder than it looks...

[eruston]

Very good explanation. I remember in C++, for every constructor, you have to have a destructor, otherwise the objects will 'pile up' on the heap = memory leak.

[JuanFVasquez]

Wow Max, I thought I knew what primitive and reference types were. You simply took these concepts to a whole new level! I didn't know about the stack and the heap at all! Thanks for explaining these amazing concepts.

[RaterisimoCBA]

Awesome video, came here because in your Udemy course about Angular you said we should look this subject up (Primitive values vs Reference values). I think I got the main ideas pretty well, I followed your coding in JSbin myself. Thanks Max !

[sydneyhill]

The stack and heap explanation and illustration for these concepts made lightbulbs go off for me. Thank you.

[cdac]

This is the best and most concise explanation I have seen on YouTube. Thanks

[ihortsarenko]

amazing as always. Thank you, Max. Maybe it could be a little bit hard for newbies, but that's the best explanation I saw for about a year of learning JS

[Concentrum]

I'm impressed by your fluent and well-prepared explaining. your gestures are also very entertaining haha, thanks for doing what you do.

[berkan]

Brother ! I really respect you. You are the best educator of all time. If you weren't born i couldn't understand these things because there is noone explain these things very specific and easy as you. Thanks

[naqeeburrahman]

That makes sense. thank u.
Earlier I was bit confused why u took long steps to copy in one example of your react course.

[tezdogs]

This actually helped me understand how to use pointers and reference values in C++, too!
Thank you Max! :D

[dhanooshbargav]

You did the explanation as best as you could. Thanks a lot!