so many things here. I would like to sum up in notes, -> let and const are hoisted. we cant use them before initialization is result of "temporal dead zone". -> js use diff memory than global execution context to store let and cost. which is reason behind "temporal dead zone" -> level of strictness ... var
Things learned: 1. let and const are hoisted but its memory is allocated at other place than window which cannot be accessed before initialisation. 2. Temporal Dead Zone exists until variable is declared and assigned a value. 3. window.variable OR this.variable will not give value of variable defined using let or const. 4. We cannot redeclare the same variable with let/const(even with using var the second time). 5. const variable declaration and initialisation must be done on the same line. 6. There are three types of error: [1] referenceError {given where variable does not have memory allocation} [2] typeError {given when we change type that is not supposed to be changed} [3] syntaxError {when proper syntax(way of writing a statement) is not used}. 7. Use const wherever possible followed by let, Use var as little as possible(only if you have to). It helps avoid error. 8. Initialising variables at the top is good idea, helps shrinks TDZ to zero.
@vipin here you are re initializing it and that is allowed in let but you cannot redeclare the same variable again. I hope this was what you were looking for.
I am 3 years of experienced react native developer. I learn JS from many youtubers, udmy plans many more but this is what i was looking for since 3.5 years. Dear new learner's you can blindly follow this guy. Really a gem 💎
Next Video: let & const Block Scope and Shadowing in JS 🔥 - th-cam.com/video/lW_erSjyMeM/w-d-xo.html How was this video? Are you feeling excited? Let me know in the comments below. ❤️
Sir can you tell these videos are Beginners who wanna crack Js interviews or for those who just want to understand Js for web development and pickup any Js framework with ease? I just wanna know the target audience. Btw love the explanations!🙏
Hi Akashay , do interviewer ask about design pattern ? How important they are for a senior js developer and can you please upload something on design pattern . They are so confusing .. It will be a great . Thank you sir for your work i am following you from last one year your first vedio is the pivot point in my career
Everytime see your video always learn something new... like in this video temporal dead zone. You are doing good work keep it up. Big big big thanks from my side.😍
Sir one request please try to complete this series by November end if possible it will be very benifitial for me for my placement interviews as you cover everything in very detailed way which is not available anywhere else
I think I was in " temporal dead zone " until this video was completed 🙏😀🙏 Thank you so much all other concept I learned before strat watching your video made me fell now that I was in "Temporal dead zone". I really love having these concepts over watching movies and series on Netflix, you making my interest going far and far Brother. ❤️I ALREADY FALL IN LOVE WITH JAVASCRIPT ❤️JUST BECAUSE OF YOU BROTHER period.
I have been studying these concepts for the past few weeks and was already starting to feel stuck, until I found your videos by chance. His explanation is impeccable. I'm following this playlist firmly. Thanks!
dude namaste js is free or there is paid version also of namaste js??and is this js series complete or incomplete ...is namaste js series a complete series of js topics??
I have been studying these concepts last one year but now I understood all Advance JS concepts through visualization . Thanks . your efforts are appreciable .
i was really confused about let and const hoisting when my trainer asked me. And your video explained everything about it . Now am confident about these concepts. Thank you namasthe js
Here is the full notes of the video : 1. "let" and "const" declarations are hoisted, but they are hoisted very differently from the "var" declarations. 2. Memory is assigned to "var" declarations, and "var" declarations are always attached to the global object "window". In case of "let" and "const", they are allocated memory in some different memory space other than global space known as "Script", and this is what we call hoisting. The "let" and "const" declarations are not attached to the global object "window". And this is the reason you cannot access these "let" and "const" variables before you have put some value in them. 3. Temporal dead zone is the time since when "let" & "const" variables were hoisted (set as "undefined") and till it is initialized with some value, the time between these two phenomena's is known as the Temporal Dead Zone. Whenever you try to access a "let" or "const" variable in the temporal dead zone, then it will always give you reference error. 4. var declarations are always attached to the window object, provided they've been declared in the global scope. let and const declarations are never attached to the window object, as these variables are never stored in the global memory space. 5. let and const are more strict than var. Re-declaration of let is not allowed in JS. The JS engine will give a syntax error, it is not allowed in the same scope. 6. How to avoid temporal dead zone? Sometimes the temporal dead zone can mess our code as a developer. The best way to avoid the temporal dead zone is to always put your declarations and initializations on the top of the code. So, that as soon as your code starts running, it hits the initialization part at the first, and then you go into the logic, and then you do something with these variables. Otherwise, you'll run into unexpected errors in your code. This way we're shrinking the temporal dead zone nearly to zero. We've minimized the TDZ nearly to zero, while moving all the initializations at the top, so that nothing happens before these initializations.
All your videos help me out discover many new things which I could have never figured out by myself at this particular time. Thanks alot, Akshay. 🤩 DOUBT: let and const refer to Script, right! So what's the relation between Script and Window? Because we can reassign values to let objects into the functions defined in Window scope.
These are insane teaching skills. I have been dropped in 3 interviews bcs of scope output questions. Now, i explain then how sizes are allocated within different scopes.
Temporal dead zone is the time between the variable scope creation and its initialisation, that is why let,const will throw error when they are put outside of some blocks (i.e. global context which is not lexical), that is why if you just surround let, const with blocks then their scope will be a block scope and its created and then they wont throw error coz now your accessing them after the time of their scope creation
one of great videos that i have seen on JavaScript, before coming to this channel i was searching on udemy, LinkedIn learning for the best courses, but i found this course, from that day i have never searched for any other course Thank you Akshay Saini for wonderful content....🤗🤗🤗 Try to make some videos on JavaScript logical questions, so that it helps us to understand these concepts in a practical way Today I Got my offer letter because of your videos....
Lots to learn from this video. Would like to add a small detail: If they(let and const) are declared in a block, they don’t get hoisted at all, they will get memory allocation(not assignment) when their block actually starts during execution phase. Try the function below and notice the memory allocation in dev tools function abc(){ debugger; var a=10; let b=20; const c=30; if(true){ debugger: var x=10; let y=20; const z=30; } }
Finally got relief 😁 . Daily twice when I woke up I I'll check the channel for new video and when I am going to bed again I I'll do the same . Please upload daily bro 😑😑😑.
Apologies brother, I got busy with the festivals and was not able to make new videos. Thank you for so much excitement, it motivates me to make more videos quickly. ❤️ I'm trying my best, but still cannot make one video in a day along with my job. It takes a lot of time to prepare content, then record video, then edit the video and then upload and release it. Somtimes, if the video doesn't come out good, I have to reshoot that part. It takes time. But I'll try my best to come back as fast as possible. Thank you for your support. 😇
@Akshay Saini Love your efforts & yeah it's not easy to dive deep into these concepts and make a video every day! More power to you man! Take care. I'm really liking your way of teaching.
I came from swift and PHP background and I clearly understand Javascript with you exceptional teaching. Thanks for the videos. Looking forward to other videos.
Bhai bhai bhai.....What a concept clearance man🙌🏻. I took udemy courses of 50hr messed up duration but the core fundamentals are here in just 5 hrs for free. Thats the difference
Before watching these videos I could write basic javascript code but I didn't know these important things. Now I think theses are the most important things which should be known to us. So Thank you very much sir❤❤.
This is literally the best explanation of Hoisting & errors for var, let and const in the world. Why is it sometimes 'is not defined ' and ' Reference Error cannot access before initialization '? The error message shows differently with the same code. Are they the same thing? ex) console.log(a); // is not defined or cannot access before initialization let a = 10;
@4:20 Hey bro! Really enjoying this indepth content for javascript! I just wanted to point out a small error, You said that it is not possible to access the let and const declarations before you put some value in them. Well you could access let variables memory space without putting any value in them provided that it precedes the usage of the variables: let a; console.log(a); a=10; output=> undefined
good catch indeed. I have a tentative explanation. what if 'a' that we are accessing is not the one declared with let but the one which we attach to global 'window' object. see. console.log(window.a) outputs 'undefined' as well. here we didn't declare any 'a' with let.
As I am a web designer I should have knowledge about all JS frame work but I have less knowledge in JS. But now I falling in love with this after wathich your videos, and practising accordingly.Best teacher ever. Thank you very much
Boy this stuff is truly amazing and is super valuable! These are the missing parts I never really understood and understanding those concepts makes everything about JavaScript so much easier and clearer.
A small fact I would like to point out is instead of saying let should be initialized, we need to say declared. What I mean is console.log(a) // Would throw ReferenceError here let a; console.log(a); // will print undefined , same as var a = 'Hi'; console.log(a); // will print Hi Great Video
i have been struggling so many years to fix how things happened behind the screen but now its very clear to me . became a big fan of yours .. thanks a lot .
every time i think that its just a basic video and i know all about this topic, but after watching your video on same topic i found that there are tons of things to learn which were abstracted in our day to day work
Till date..in every interview I have answered to interviewer that var is hoisted and let and const are not hoisted😅....because in youtube and web people told the same🤣....Awesome video Akshay Bhai🤟🤟👍...eagerly waiting for next video
Hi @akshaymarch7, One correction is there for the temporal dead zone, it is not mandatory to assign a value if use let for declaring a variable. . So temporal dead zone exists until variable is declared that's it. Without assign value we can access it. Even I learn this from your video only so thanks to you .
1. console.log(a1); 2. let a1; here a1 in line 1 is in TDZ, as u said Without assign value we can access it. but we cant access it as it is giving ReferenceError
For revision: always keep your variable declaration on top! on top! is 'let' and 'const' functions are hoisted? > Yes (but in temporal dead-zone) take a sample program console.log(b); let a= 10; var b= 100; we made var declaration to 'b' and let to 'a' and here comes the difference: the var declaration will come under global declaration and let declaration in script (separate memory space) and these variables are not accessible unless they are assigned with certain values so the temporal dead zone is the time between saving variables in memory-space and actually value assigned to it by engine itself. In this time frame you can't access the variable, by hoisting, Engine stores the Variable in 'Variable environment'(Memory component) and until the line where the actual variable is assigned to its value (until then variable, remains in temporal dead zone) ReferenceError cannot access before initialization : avoided the concept of temporal Dead zone, bound you will get this error! Q)How it differs from "Uncaught ReferanceError : X is not defined at .js" ? A> so it comes to a question "is variable X is in Variable environment ?" >> if(true); { console.log("cannot access before initialization"); console.log("This is temporal dead zone case"); }
if(false); { console.log("Uncaught ReferanceError : X is not defined at.js"); console.log("Variable is simply not available"); }; Q) and what about variable declared by 'var'? > they will assigned 'undefined' until a value is assigned Declaration Type var = saved in Global execution context, can be assigned later and modified in script. let = saved in script execution context, temporal deadzone affects it and can later modified in script. const= saved in script execution context, temporal deadzone affects it and must be defined (assign values) when defining variable by it (cannot remained as 'undefined').
I love your depth knowledge of java script. "use const first and then let for variable declarations in day to day coding" this should be followed by every js developer.Hats off for your efforts to make this kind videos.👌👌👌👌
"temporal dead zone" is the time since when the let variable is hoisted and till it is initialized to some value, the time between that is known as the temporal dead zone.
Earlier in the past everytime I will read the documents to understand the concept of let,var and const but after seeing this video and writing down the notes shrinked the repeated effort.Amazing content.
Man O Man! I was confused between let, const, and var also even if they are hoisted or not? This video cleared my each and every doubt about them. Not just this but all the videos have solved all my doubts. Thank you so much for this. We have such a good playlist to watch and learn, I wonder how did you learn all these things in such depth.
I am very grateful for your videos, Akshay Saini! *below is a personal note to myself 1) compilador aloca espaço na memória para as declarations (var, let, const, function declaration, e class declaration), isso se chama hoisting. 2) enquanto var é indexada no objeto global, let e const ficam na temporal dead zone 3) por estar no objeto global, o acesso à var é permitido, entretando seu valor é undefined até ocorrer o assignment 4) enquanto não ocorrer o assingment à let e const, elas continuam na temporal dead zone, e enquanto estão neste local, o acesso à estas declarations é impedido (unitialized)
Temporal dead zone is like a coma state , its there but you cannot talk to him, till the time he/she has been given value of life, Great explanation , we all owe you for deep diving into Concepts
I have been watching your videos from the beginning and taking notes.Completely addicted to these videos to that level even though I’m doing other works the concepts are running at the back of my head.Thanks brother
I completely understand how the temporal dead zone is working. I am getting more confident after looking at your javascript videos. Thanks for this wonderful video. 🙏🙏
Sir your way of explaining the very difficult topic to the very least difficult way is beyond imagination i have also seen your namaste react and really got to learn a lot thank you so much...........
No webseries watching , now watching only Namste Javascript Series , Thanks Akshay Saini no one can explain this thing in a very easy manner , learned lots of new things and fundas
1st of all I would like 2 tell you tht this is mah 1st TH-cam commnt in my entire life regarding any topic. Now coming 2 the main point, I must appreciate your intention and your passion towards technology and javascript Community. It will be a great experience to see you as it is in upcoming years. Best wishes nd Standing Respect 2 your thought process and energy to serve community..🙏👍
Awsm Akshay sir! I am 30 years old and trying to enter in React js field and really ur videos are very helping me. You r doing very divine job may God bless you❤️🙏😇
Thankyou for explaining in so deep M a developer and start learning js I scroll so many videos on TH-cam but all follows the same pattern like class teacher did in college time😀 No one covers this much deeper Thanks a lot Akshay🙂🙂🙂
Amazing and loved the way you explained the concept with that depth. I am not from a CS background but i am learning full stack development. I found your playlist about a month ago and i just loved it. I rewatch many of your videos just to revise the concept. Thanks for this series. Really amazing work.
Never really knew earlier why do we get those reference errors. This video has given me the answer after 3 years of using them. Keep up the good work and keep sharing your tutorials brother!
i currently enrolled reactjs course from udemy in excitement and was not understanding core concepts of js and thought i wasted my money, then i found ur vids now course again feels worth and understandable, thank you for the great explaination
If anyone wakes me up and ask me all these questions, I can confidently answered them even if I'm in deep sleep, I'm very dumb in Javascript but because of your way of explanation I fell in love with JS❤ and with your teaching❤😍
Love the series Akshay ...... Been trying to shift to JS from Java and this series helps me understand how JS execution works like a breeze .Thank you for taking out time to do this. Helping a lot ❤️
As you explained const we should use in first place when we don't have to change the value frequently. But same thing is happening with let also.We can't redeclare let again.
so many things here. I would like to sum up in notes,
-> let and const are hoisted. we cant use them before initialization is result of "temporal dead zone".
-> js use diff memory than global execution context to store let and cost. which is reason behind "temporal dead zone"
-> level of strictness ... var
thanks
@Akshay Saini pin this comment
Just one correction let variable can be reinitialize.
@@deependrakumar2019 thanks for the notes :)
Thank you
Things learned:
1. let and const are hoisted but its memory is allocated at other place than window which cannot be accessed before initialisation.
2. Temporal Dead Zone exists until variable is declared and assigned a value.
3. window.variable OR this.variable will not give value of variable defined using let or const.
4. We cannot redeclare the same variable with let/const(even with using var the second time).
5. const variable declaration and initialisation must be done on the same line.
6. There are three types of error: [1] referenceError {given where variable does not have memory allocation} [2] typeError {given when we change type that is not supposed to be changed} [3] syntaxError {when proper syntax(way of writing a statement) is not used}.
7. Use const wherever possible followed by let, Use var as little as possible(only if you have to). It helps avoid error.
8. Initialising variables at the top is good idea, helps shrinks TDZ to zero.
Very Good Explaination
Awesome Summary just like the video
Bravo!
@vipin here you are re initializing it and that is allowed in let but you cannot redeclare the same variable again. I hope this was what you were looking for.
@@gulz4u let variable value can change without using let word again
eg: let a=10;
a=20;
I am 3 years of experienced react native developer. I learn JS from many youtubers, udmy plans many more but this is what i was looking for since 3.5 years.
Dear new learner's you can blindly follow this guy. Really a gem 💎
This is the best charity anyone can give. Thank you for not charging for these videos.
Can't believe instead of Netflix I am watching javascript videos in free time...
Same. Had plans for RAY on this weekend. Ending up watching 5 videos of this series.
surely with no credit card 😬
Much more valuable use of your time, id say
same here
This playlist is pure gold
I really feel proud cos now we don't need to refer any tutorial form foreigner while we have best talent like Akshay. Salute bro.
I failed in around 10 interviews last year but by just going through 4 vedios of yours ,I cracked the technical round and got selected. Thank you
if you donot mind mentioning those 10 faileinterview company names, we will apply now??
Next Video: let & const Block Scope and Shadowing in JS 🔥 - th-cam.com/video/lW_erSjyMeM/w-d-xo.html
How was this video? Are you feeling excited? Let me know in the comments below. ❤️
Sir can you tell these videos are Beginners who wanna crack Js interviews or for those who just want to understand Js for web development and pickup any Js framework with ease? I just wanna know the target audience. Btw love the explanations!🙏
plz Bhaiya jaldi jaldi videos upload kijiye ... i m so excited to learn JS properly.
Hi Akashay , do interviewer ask about design pattern ? How important they are for a senior js developer and can you please upload something on design pattern .
They are so confusing ..
It will be a great .
Thank you sir for your work i am following you from last one year your first vedio is the pivot point in my career
Everytime see your video always learn something new... like in this video temporal dead zone.
You are doing good work keep it up.
Big big big thanks from my side.😍
Sir one request please try to complete this series by November end if possible it will be very benifitial for me for my placement interviews as you cover everything in very detailed way which is not available anywhere else
Basically am a java developer I never really liked js, but u just made me start loving it... ಧನ್ಯವಾದಗಳು❤️
Same here... so much frustration.
I think I was in " temporal dead zone " until this video was completed 🙏😀🙏
Thank you so much all other concept I learned before strat watching your video made me fell now that I was in "Temporal dead zone".
I really love having these concepts over watching movies and series on Netflix, you making my interest going far and far Brother.
❤️I ALREADY FALL IN LOVE WITH JAVASCRIPT ❤️JUST BECAUSE OF YOU BROTHER period.
PUN at its best
😀
I have been studying these concepts for the past few weeks and was already starting to feel stuck, until I found your videos by chance. His explanation is impeccable. I'm following this playlist firmly. Thanks!
dude namaste js is free or there is paid version also of namaste js??and is this js series complete or incomplete ...is namaste js series a complete series of js topics??
I guess if u take any JS interview then nobody in this world would get hired .Absolutely amazing tutorials bro .Keep going 😊😊😊
Haha, nothing like that brother.. 😅
No, Not like that
I think he will hire the best person...
😂😂
We can clear his interview after watching all his videos 🤣
@@mahimak5736 he be like:Mera maal mere ko hi bech rha
I have been studying these concepts last one year but now I understood all Advance JS concepts through visualization . Thanks . your efforts are appreciable .
i was really confused about let and const hoisting when my trainer asked me. And your video explained everything about it . Now am confident about these concepts. Thank you namasthe js
Here is the full notes of the video :
1. "let" and "const" declarations are hoisted, but they are hoisted very differently from the "var" declarations.
2. Memory is assigned to "var" declarations, and "var" declarations are always attached to the global object "window". In case of "let" and "const", they are allocated memory in some different memory space other than global space known as "Script", and this is what we call hoisting. The "let" and "const" declarations are not attached to the global object "window". And this is the reason you cannot access these "let" and "const" variables before you have put some value in them.
3. Temporal dead zone is the time since when "let" & "const" variables were hoisted (set as "undefined") and till it is initialized with some value, the time between these two phenomena's is known as the Temporal Dead Zone. Whenever you try to access a "let" or "const" variable in the temporal dead zone, then it will always give you reference error.
4. var declarations are always attached to the window object, provided they've been declared in the global scope. let and const declarations are never attached to the window object, as these variables are never stored in the global memory space.
5. let and const are more strict than var. Re-declaration of let is not allowed in JS. The JS engine will give a syntax error, it is not allowed in the same scope.
6. How to avoid temporal dead zone?
Sometimes the temporal dead zone can mess our code as a developer. The best way to avoid the temporal dead zone is to always put your declarations and initializations on the top of the code. So, that as soon as your code starts running, it hits the initialization part at the first, and then you go into the logic, and then you do something with these variables. Otherwise, you'll run into unexpected errors in your code.
This way we're shrinking the temporal dead zone nearly to zero. We've minimized the TDZ nearly to zero, while moving all the initializations at the top, so that nothing happens before these initializations.
Watching whole series the second time just before my interview ❤️
All your videos help me out discover many new things which I could have never figured out by myself at this particular time. Thanks alot, Akshay. 🤩
DOUBT:
let and const refer to Script, right! So what's the relation between Script and Window? Because we can reassign values to let objects into the functions defined in Window scope.
These are insane teaching skills. I have been dropped in 3 interviews bcs of scope output questions. Now, i explain then how sizes are allocated within different scopes.
Temporal dead zone is the time between the variable scope creation and its initialisation, that is why let,const will throw error when they are put outside of some blocks (i.e. global context which is not lexical), that is why if you just surround let, const with blocks then their scope will be a block scope and its created and then they wont throw error coz now your accessing them after the time of their scope creation
Temporal dead zone: Time gap between the variables hoisted and its initialization, Understood clearly about it Thank you Akshay Stay blessed :) :)
Shouldn't it be declaration instead of initialisation ?
@@vishalgoel6323 It should be initialisation only.
The legend of JavaScript..no one can teach us in such a intricate details in this world..lots of love and respect for you brother 🙏🙏..
Instead of buying any course i will learn from your videos
Thanks for sharing such valuable knowledge bhai
This tutorial is the best for the beginners, because it laterally makes coding fun!!..........Are you going to make any content on ES6 and react??
Seriously you are very good at explaining the difficult concepts with live examples
one of great videos that i have seen on JavaScript, before coming to this channel i was searching on udemy, LinkedIn learning for the best courses, but i found this course, from that day i have never searched for any other course
Thank you Akshay Saini for wonderful content....🤗🤗🤗
Try to make some videos on JavaScript logical questions, so that it helps us to understand these concepts in a practical way
Today I Got my offer letter because of your videos....
Wow, Congratulations brother! ❤️
Lots to learn from this video. Would like to add a small detail:
If they(let and const) are declared in a block, they don’t get hoisted at all, they will get memory allocation(not assignment) when their block actually starts during execution phase. Try the function below and notice the memory allocation in dev tools
function abc(){
debugger;
var a=10;
let b=20;
const c=30;
if(true){
debugger:
var x=10;
let y=20;
const z=30;
}
}
Finally got relief 😁 . Daily twice when I woke up I I'll check the channel for new video and when I am going to bed again I I'll do the same . Please upload daily bro 😑😑😑.
Apologies brother, I got busy with the festivals and was not able to make new videos.
Thank you for so much excitement, it motivates me to make more videos quickly. ❤️
I'm trying my best, but still cannot make one video in a day along with my job. It takes a lot of time to prepare content, then record video, then edit the video and then upload and release it.
Somtimes, if the video doesn't come out good, I have to reshoot that part. It takes time.
But I'll try my best to come back as fast as possible.
Thank you for your support. 😇
@@akshaymarch7 thank you for your efforts, still I will be checking your channel is there any new video ❤️❤️❤️
@Akshay Saini Love your efforts & yeah it's not easy to dive deep into these concepts and make a video every day! More power to you man! Take care. I'm really liking your way of teaching.
Hello @@akshaymarch7, can you please make a video series on backend(.net c#, mvc controller) web development as well . Your explanation is amazing.
I came from swift and PHP background and I clearly understand Javascript with you exceptional teaching. Thanks for the videos. Looking forward to other videos.
Bhai bhai bhai.....What a concept clearance man🙌🏻. I took udemy courses of 50hr messed up duration but the core fundamentals are here in just 5 hrs for free. Thats the difference
Not everything which is Free is useless ❤️
Before watching these videos I could write basic javascript code but I didn't know these important things. Now I think theses are the most important things which should be known to us. So Thank you very much sir❤❤.
Didn't heard about this terminology "Temporal Dead Zone" before but now I know it and can explain to anybody because of the great Mr.Akshay 😃
This is literally the best explanation of Hoisting & errors for var, let and const in the world.
Why is it sometimes 'is not defined ' and ' Reference Error cannot access before initialization '?
The error message shows differently with the same code.
Are they the same thing?
ex)
console.log(a); // is not defined or cannot access before initialization
let a = 10;
I have never come across such high-quality content on JS. Thanks for digging so deep.
The level of understanding you have is mind blowing.
@4:20 Hey bro! Really enjoying this indepth content for javascript! I just wanted to point out a small error,
You said that it is not possible to access the let and const declarations before you put some value in them. Well you could access let variables memory space without putting any value in them provided that it precedes the usage of the variables:
let a;
console.log(a);
a=10;
output=>
undefined
Good catch.
Not that this is for let only. For const, since we hv to initialize them during declaration this wont be possible.
good catch indeed. I have a tentative explanation.
what if 'a' that we are accessing is not the one declared with let but the one which we attach to global 'window' object. see.
console.log(window.a)
outputs 'undefined' as well.
here we didn't declare any 'a' with let.
@@ycombinator765 exactly, it's like declaring a new variable
As I am a web designer I should have knowledge about all JS frame work but I have less knowledge in JS. But now I falling in love with this after wathich your videos, and practising accordingly.Best teacher ever. Thank you very much
Boy this stuff is truly amazing and is super valuable! These are the missing parts I never really understood and understanding those concepts makes everything about JavaScript so much easier and clearer.
A small fact I would like to point out is instead of saying let should be initialized, we need to say declared. What I mean is
console.log(a) // Would throw ReferenceError here
let a;
console.log(a); // will print undefined , same as var
a = 'Hi';
console.log(a); // will print Hi
Great Video
i am addicted to this series! Can't wait for next one! Making notes with every episode :)
Oh, wow! That's great, it's a very good way to remember things. 😇
kya aap notes send kar sakte hai
i have been struggling so many years to fix how things happened behind the screen but now its very clear to me . became a big fan of yours .. thanks a lot .
Without watching video first I like the video
Always love ur video with good information
Thank you so much, @Shreedevi. It means a lot. ❤️
This is the best JavaScript course, I really wonder how did you learnt so much deep.
Just a request , after completing this course could you explain how css works in detail ! Amazing content as usual
Can I
Added to my list, will try to cover that also. 😇
@@akshaymarch7 Is it still on list?
@@akshaymarch7sir hope ur list will be made soon
That explanation and coding demo of ReferenceError, TypeError, SyntaxError was amazing
Make more videos on js concept for interview perspectives. The way you explain everything was great!
Thank you so much, Varnika. Your comment motivates me to make more videos. ❤️
Dude...You nailed it.. Itna acha clear explaination h.....jitne bhi JS k videos dekhe usme se tumhare video k level ka koi bhi nai match kr paya.
😇
I genuinely appreciate your efforts of making the concepts clear to us.. thank you so much for the series, I'm learning a lot
every time i think that its just a basic video and i know all about this topic, but after watching your video on same topic i found that there are tons of things to learn which were abstracted in our day to day work
Till date..in every interview I have answered to interviewer that var is hoisted and let and const are not hoisted😅....because in youtube and web people told the same🤣....Awesome video Akshay Bhai🤟🤟👍...eagerly waiting for next video
I see a lot of people doing that. 😅
But don't worry, now you know what to answer. 😉
Hi @akshaymarch7,
One correction is there for the temporal dead zone, it is not mandatory to assign a value if use let for declaring a variable. . So temporal dead zone exists until variable is declared that's it. Without assign value we can access it. Even I learn this from your video only so thanks to you .
1. console.log(a1);
2. let a1;
here a1 in line 1 is in TDZ, as u said Without assign value we can access it. but we cant access it as it is giving ReferenceError
For revision:
always keep your variable declaration on top! on top!
is 'let' and 'const' functions are hoisted? > Yes (but in temporal dead-zone)
take a sample program
console.log(b);
let a= 10;
var b= 100;
we made var declaration to 'b' and let to 'a' and here comes the difference: the var declaration will come under global declaration and let declaration in script (separate memory space) and these variables are not accessible unless they are assigned with certain values
so the temporal dead zone is the time between saving variables in memory-space and actually value assigned to it by engine itself. In this time frame you can't access the variable, by hoisting, Engine stores the Variable in 'Variable environment'(Memory component) and until the line where the actual variable is assigned to its value (until then variable, remains in temporal dead zone)
ReferenceError cannot access before initialization : avoided the concept of temporal Dead zone, bound you will get this error!
Q)How it differs from "Uncaught ReferanceError : X is not defined at .js" ?
A> so it comes to a question "is variable X is in Variable environment ?"
>> if(true);
{
console.log("cannot access before initialization");
console.log("This is temporal dead zone case");
}
if(false);
{
console.log("Uncaught ReferanceError : X is not defined at.js");
console.log("Variable is simply not available");
};
Q) and what about variable declared by 'var'?
> they will assigned 'undefined' until a value is assigned
Declaration Type
var = saved in Global execution context, can be assigned later and modified in script.
let = saved in script execution context, temporal deadzone affects it and can later modified in script.
const= saved in script execution context, temporal deadzone affects it and must be defined (assign values) when defining variable by it (cannot remained as 'undefined').
Write a blog brother, this effort of yours might get lost in so many comments.
BTW love your dedication, you're a gem! 💥
thank you ♥
I love your depth knowledge of java script. "use const first and then let for variable declarations in day to day coding" this should be followed by every js developer.Hats off for your efforts to make this kind videos.👌👌👌👌
Thank you so much for your comment, Vinod. It motivates me. 😇♥️
"temporal dead zone" is the time since when the let variable is hoisted and till it is initialized to some value, the time between that is known as the temporal dead zone.
Your explanations changed my view point of javascript. . . From hating it i have started loving it.
#LovingIt.
When I read this concept in book, then I am bored but today I am not bored.
Earlier in the past everytime I will read the documents to understand the concept of let,var and const but after seeing this video and writing down the notes shrinked the repeated effort.Amazing content.
I literally started dancing on the tune at the end.😂
every songs in the end of video hear like word namaste javascipt lyrics with superb music tone
.
Man O Man! I was confused between let, const, and var also even if they are hoisted or not?
This video cleared my each and every doubt about them. Not just this but all the videos have solved all my doubts.
Thank you so much for this. We have such a good playlist to watch and learn, I wonder how did you learn all these things in such depth.
yes sir! I understood the temporal dead zone very clearly. thank you a lot sir and Very happy diwali.
Happy Diwali Afaque. 😇
@@akshaymarch7 thank you so much sir..Nobody teaches with such depth
I am very grateful for your videos, Akshay Saini!
*below is a personal note to myself
1) compilador aloca espaço na memória para as declarations (var, let, const, function declaration, e class declaration), isso se chama hoisting.
2) enquanto var é indexada no objeto global, let e const ficam na temporal dead zone
3) por estar no objeto global, o acesso à var é permitido, entretando seu valor é undefined até ocorrer o assignment
4) enquanto não ocorrer o assingment à let e const, elas continuam na temporal dead zone, e enquanto estão neste local, o acesso à estas declarations é impedido (unitialized)
Waited for long😍
Temporal dead zone is like a coma state , its there but you cannot talk to him, till the time he/she has been given value of life, Great explanation , we all owe you for deep diving into Concepts
When you said let and const have block scope , block scope, block sock, it sounded like mujhe drugs do, drugs do , drugs do :P
😅
I have been watching your videos from the beginning and taking notes.Completely addicted to these videos to that level even though I’m doing other works the concepts are running at the back of my head.Thanks brother
I'm studying at a Computer Science School, and I told all other students about this channel, Namaste JavaScript ))))
I am becoming your admirer by watching this series because you are giving us very deep knowledge about javascript.. thanks..❤️🙏
I completely understand how the temporal dead zone is working. I am getting more confident after looking at your javascript videos. Thanks for this wonderful video.
🙏🙏
Sir your way of explaining the very difficult topic to the very least difficult way is beyond imagination i have also seen your namaste react and really got to learn a lot thank you so much...........
You have done real autopsy of Javascript. Now things are so so so easy to visualise that i dont have to remember anything.
Thank You so much!!!
No webseries watching , now watching only Namste Javascript Series , Thanks Akshay Saini no one can explain this thing in a very easy manner , learned lots of new things and fundas
I like your way pf teaching, pehli bar basic itne acche se clear ho rahe h, nice bro
I havent seen any teacher with such a enthusiasm ever. Hats off to you sir. You made our javascript journey so much easy
Wowwww.
LET,
CONST,
TEMPORAL DEAD ZONE
REFERENCE ERROR
GLOBAL OBJECT
TYPE ERROR
SYNTAX ERROR
Now I am ready for interview.
1st of all I would like 2 tell you tht this is mah 1st TH-cam commnt in my entire life regarding any topic. Now coming 2 the main point, I must appreciate your intention and your passion towards technology and javascript Community. It will be a great experience to see you as it is in upcoming years. Best wishes nd Standing Respect 2 your thought process and energy to serve community..🙏👍
Awsm Akshay sir! I am 30 years old and trying to enter in React js field and really ur videos are very helping me. You r doing very divine job may God bless you❤️🙏😇
This man is really a fantastic teacher.I congratulate you for this level of understanding and explaining.
Thankyou for explaining in so deep
M a developer and start learning js
I scroll so many videos on TH-cam but all follows the same pattern like class teacher did in college time😀
No one covers this much deeper
Thanks a lot Akshay🙂🙂🙂
Yahoo baba, code with Harry , hitesh choudhary, Akshay saini javascript master teacher❤
briliantly explained concepts. I have just understood hoisting perfectly
After a long time now I can saw I have the clarity between const, let and var. Thanks for the video.
Amazing and loved the way you explained the concept with that depth.
I am not from a CS background but i am learning full stack development. I found your playlist about a month ago and i just loved it.
I rewatch many of your videos just to revise the concept.
Thanks for this series.
Really amazing work.
content - amazing
energy - hats off
music at the end - vibe he
Aap samjhao aur hume samjh na aaye aisa ho sakta hai love u sir for the knowledge you are sharing
Never really knew earlier why do we get those reference errors. This video has given me the answer after 3 years of using them. Keep up the good work and keep sharing your tutorials brother!
You really weren't kidding when you said "Let me tell you something interesting"
Good stuff..Learned a lot from this video
seen playlist of other tutors but Akshay gives the best clarity. Thanks man
i currently enrolled reactjs course from udemy in excitement and was not understanding core concepts of js and thought i wasted my money, then i found ur vids now course again feels worth and understandable, thank you for the great explaination
If anyone wakes me up and ask me all these questions, I can confidently answered them even if I'm in deep sleep, I'm very dumb in Javascript but because of your way of explanation I fell in love with JS❤ and with your teaching❤😍
Love the series Akshay ...... Been trying to shift to JS from Java and this series helps me understand how JS execution works like a breeze .Thank you for taking out time to do this. Helping a lot ❤️
just love this video.......................firstly i was very confused with scope of let and var but after seeing this video all my doubts are cleared
I love the way you are teaching...lots of love from my side...
As you explained const we should use in first place when we don't have to change the value frequently. But same thing is happening with let also.We can't redeclare let again.
very well understood the temporal dead Zone concept, and your smile gives me the positive vibes
no one teachers these concepts clearly..
thanks for these videos bhaiya..
never seen such kind of explanation ever before in any tutorial. You are truly a gem. Thanks for making this amazing series. May God bless you
Understood the basics very well explanation!!! Namaste Javascript
Aapka javascript lecture bole to Ek no Sir
Kya aap Angular ke liye video bna sakte h sir
I was already in love with JS... but i was unaware of these concepts...Ek tarfa pyaar ko do tarfa kardia aapne...A Huge Thanks!!!
brother your way of explaing is far good as compare to any another youtube i am viewing your video after 2 yr but the way is non comparable to another