TO say thank you will not do justice with your teaching. I have never learnt coding easily before watching your videos. You are a great mentor. Keep it up.

Good tutorial. What would be great is if you explained not only what Maps and WeakMaps are, but when and why you would use them over a traditional object.

0:50 every time i watch your video when you say *"techsith tutorials"* it feels me like that you are saying *"Taxi Tutorials"* and then i smile :)

Man you just explain things really simply.. loved you're videos ❤

Hi bro, last 3 days I watching ur interview solve question in js and ur all video. It's really helpful, yesterday I attend the interview in CTS, it very helpful for me , keep going bro...

Genuine efforts. Thanks

You are a Genius , there is so many materials out there but just make it easy...Thank you

2:44 JavaScript Object not support any Object as key. It parse an Object toString(), and treat '[object Object]' as key

Very nice and simple example at the end about the difference between a map and a weakmap. This helped me tremendously to understand. Thank you

awesome tutorial again..you are a genius.

you explain in very simple way which make easy to understand.Thanks a lot

Another great video as always! Thank you for taking the time to make this and share it with all of us! Near the end of the video, you had a small homework assignment, I want to take a guess as to why the value remained... I suspect when it was initially created using var the value got attached to the global space, additionally I think when creating the map or the weak map using const or let will keep the value contained inside the function scope. Please let us know if you post an answer to the question you raised. As always thumbs up and I am subscribed with notifications turned on, I don't want to miss any videos from your channel!

Again a masterpiece !!!!

TY!

Answer to you question: x was not garbage collected , it will stays there until console refreshed or you forcefully delete it from map

liked as always before watching :-)

soo good, please carry on ..

It helps me a lot to learn js concept thanks for this amazing videos.

thanks, please make a video related to how dispatch works in react-redux

thx, very good explanation

Good explanation.

its nice that we can make object a key but my question is why would anyone ever wanna do that ?

I have a question: I see that it's interesting that maps allow us to pair an object to any other value. That is cool and all, but why would I do that if I can simply assign the value as a property of the object I want to pair it with? The only reason I can think of is to free the object of the value in question in case I ever want to iterate through it with a for in loop or something. Also you mentioned you would like your videos translated to other languages. I'm about to resume classes at college right now, but I might try to give you translated transcripts in Portuguese (Brazilian) of a few videos every now and then, with the only problem being syncing everything (I have no experience in this). Would unsynced transcripts be of any help?

I have said many time - Thank you and God bless you. What I would criticize here is that in practice you would have a simple (primitive usually) key and perhaps object value. Your examples were the other way around and that gave me a vertical head spin :) . Also I came to learn what those WeakMaps are and why I would need them and yet I got nothing except that they do not hold garbage collected keys in weird example.

this guy rocks!

This is good :)

The one thing that I like about you is the detail of your tutorials. I cannot figure out how you learn these things with such details. Can you tell what resources you use to learn these things. Thanks for the video SIR

WeakMaps will not retain entry because it only saves the reference where as Map actually saves a copy of the key object and so it retains even after GC. Please correct if am wrong.

This might look like it's the same as setting props on an Object but what ends up happening is you get a hash conflict. toString is used to create the key which will result in two entries with the same key ( [object Object] ). Then when you retrieve it has to iterate over all entries with this key and find the proper entry by strict equality. What this is means is that in a way of saying map.get(obj) is now an O(n) operation compared to O(1) in the case of accessing an object unless V8 internally sets the address of the object as key which would make sense. Also the reason you don't get a key in there is because the object gets garbage collected so the reference is gone. If you declare the object with var, global will keep a reference to it.

Thank you

Good tutorial

Thanks

for of is available with regular object as well , but we will have ti iterate through Object.entries(obj)

Hello @techsith.. I have read in a Medium article that keys are always coerced to strings in javascript So the object is converted into [object Object]. Even when we declare another object as a key it converts this into [object Object] and confuses to override the old one.

Great video! Thank you! Just curious on your question in the end, I am assuming that the Array memory space created during map does not exist when you change to weakmap, so it shows the updated entries. But when you start with weakmap on a new browser, it does not allocate memory space for something that does not exist, and so you don't see entries. Just a guess. Please correct me if this is wrong, would be great to know the correct answer.

I would love to understand how Javascript uses 'Garbage collection' and how to write more efficient code / debug garbage collection. Thank you for your well explained videos!

Where we use this. Plz answer

I tried with this example but I am still getting the entries when I console log weakmap ut of block

A suggestion, please make real world projects using js it would be really helpful to follow along for newbie dev. Thanks..:)

Can you please give a real world scenario where Maps are useful?

Thanks buddy

awesome explanation sir.

You can use console.table for array.

10:10 to prevent this. CAn't we just use LET instead of VAR?

I'm very late to your channel but the answer to the last part is that the previous entry will still be in memory when we run it.

What is the difference between for in loop and for of loop ??

It's nice, I have one topic, symbol() can you please explain it.

Good video to learn on map and weakMap. Regarding the question at the end, I think Map creates the copy of the object passed in key. So even when we update the value of the key object same is not getting reflected inside map key. Whereas WeakMap stores the key with referencing the object passed as key, so if its scope of object is not present it also clears the entries associated with it. But not sure why its retaining the value even after refreshing the browser. Can you please guide on this.

Its still in memory, because JS engine not taken the key in garbage collection array. Restart the browser create a new cycle of garbage collection. Please correct me if I'm wrong :)

Hello, interesting video, but I guess I am still missing a concrete example of when would need to store an object or an array as a key?

Sets and WeakSets please!

{let y1 = {a:[1,2]}; var x1 = new WeakMap(); x1.set(y1,'a')}console.log(x1) I am still getting same output as in map. not working as mentioned in example.

Hi, Thanks for the explanation, I have a question what is the use of having an object as a key?

How JS Maps differentiate between key objects? Will it use hash method like in java?

Still not understand... why we use 'Object' as a key in Map.

good but ... if you use value of a to alfa , the tutorial would be more interesting... i am a newbie so its so hard to distinguish which a is your var and which a is your object and which a is your key.....LOL...(lot of love)sir

what if? set same object as a key multiple times var map = new Map(); map.set( { name : 'Eswar' } , '100'); console.log(map.has( { name : 'Eswar' } )); //false Ideally it should be TRUE, may be i am checking with different objects but both objects contain same content. How can i solve this, In java we can handle with heshcode() & equels()

Great vids. Could you please make regex as well? ;)

what IDE are you using ? is it JSbin ?

Answer to your question at the end: WeakMap() the lexical scope of JavaScript plays a part in browser cache. once the IIFE is executed, the key and the value of that key are removed from memory because the key is taken out of scope.

Thank you so much for the information. I have one question if you could please answer You said, "for-in" loop is bad. Would you please tell us why it is bad?

I guess the answer is because the variable x in used by or have a reference to Map so WeakMap not working ... is that right ? :)

Why am i not able to run the for..of and array spread example on chrome console ?

I think you started with a very twisted example for key. You could start with simple numbers as keys and then extend in more twisted directions.

To me, it looked like key and value were switched in the Map() example

Please do video for JavaScript data structures

I couldn't find an answer to the HM question :\

Yes, react-redux please...

Maybe it's cached?

Would you ever consider doing a tutorial for making a 2d game engine?

React redux would be awesome...