Differences Between Var, Let, and Const

You have probably watched many different tutorials, and you may have noticed that some tutorials use var to declare variables while others use let or even const. It can get confusing quickly on what the differences are between the keywords, so in this video I am going to be explaining everything you need to know about var, let, and const. I will be going over their differences as well as explaining what situations you should use each keyword.
If you have any suggestions for a JavaScript topic, please let me know in the comments below.
Let vs Const vs Var Article:
blog.webdevsimplified.com/202...
Twitter:
/ devsimplified
GitHub:
github.com/WebDevSimplified
CodePen:
codepen.io/WebDevSimplified
#VarVsLet #JavaScript #WebDevelopment

[@ianoliver6828]

You have a super rare skill. It's rare to find someone who is both a skilled programmer AND a skilled teacher / communicator. Thank you for your videos

[@olegfare4625]

and Zach Efron level of handsome

[@sclutzo]

Totally agree!

[@camilafloressanhueza7966]

OMG!! I had seen 100000 videos whose explanations were extremely complicated, but you explained it in less than 5 minutes!! Thank you very much

[@GoogleAccount-jw1rd]

And understandable

[@Max-nm8ct]

Mate, I must say, your hair is on fleek!

[@TheSlimSh4dy]

Thank you for the clear explanation! Currently, I'm learning HTML, CSS & Javascript and if I don't understand something, I'm firstly looking at your channel to find an explanation. If it doesn't exist on your channel, then I'm searching in other sources. You are a very good teacher, your videos are short, consistent and very clear, without any unnecessary content. Thank you very much for sharing your time to make these videos.

[@jthomasaurus]

Another super-clear explanation. Love your video style, brevity, and way of explaining everything. Plain and simple!

[@dorothyglade9087]

This was great, you speak at just the right speed and your voice is clear. This really helped me and my husband with something in our bootcamp.

[@AidanJoyce]

Would like to say, well done and thank you for a clear and concise explanation of the similarities, differences and when to use, Var, Const and Let. Watched other videos and without doubt, you nail it better here with both explanation and example. Will be watching more of your stuff as this was a great measure stick for the quality of teaching. Keep up the great work.

[@AlexTechie]

6:36 I didn't know that. This is why I always watch your videos, even if I think I understand the subject before hand. Great work! 👍

[@WebDevSimplified]

It is a bit counter intuitive based on the name. You can use Object.freeze to create an object that cannot have the properties reassigned, but it will still let you reassign a nested property such as company.ceo.name = 'New name'

[@AlexTechie]

@@WebDevSimplified thanks for the tip! As I was watching the part I referenced earlier, I was wondering how we would assign constants to the properties of an object, so it's like you read my mind. :D

[@santra528]

This is complete explanation of let vs const vs var I have ever seen. Thanks Kyle 😊

[@raaghavendrahm4883]

I am just starting with JS and I was stuck with this like hell. You made it so clear. Thanks a lot!!

[@shantanukulkarni8883]

Basically, _let_ is _var_ done right.

[@dozadetrezire7455]

You forgot to say one more thing: when you declare a variable with var keyowrd, this automatically creates a property inside the Window ojbject.. so, if you say for example: var x = 1; and after that you say: console.log(window)... you will see that in the window object you will find the property X with the value of 1. Instead, if you declare a variable with let or const, this won't ceate a property inside the Window object. I guess this was also very important to mention!

[@pratikthorat3480]

This is the best explanation I've ever seen. I do know the differences yet I learnt something new

[@youareuglybuti]

Thank you man, was struggling to understand these basic concepts. You are a lifesaver.

[@tonic.9234]

I never knew var worked like this, and I've been using Javascript almost daily for over 2 years. I always assumed it worked like let because I have a background in other programming languages and assumed it's scoping worked the same. So wild! Thanks for the clarification!

[@rohit9969171579]

It was very crystal clear explanation thank you.

[@thecoderabbi]

Thank you very much Kyle, This is great. Very explicit. I think I would begin using the 'const' instead of the 'var' Thanks ✌️

[@jorgefrias7889]

Amazing explanation. Simple and straight to the point. Thank you!

[@dsvhs93]

Whenever Kyle comes out with the JavaScript class that he is working on.... I am purchasing it. He is awesome! Thank you Kyle!

[@WebDevSimplified]

Thank you for the support! I start recordikg tomorrow!

[@moonlightCR7]

Thanks a billion, Kyle for explaining the difference among these keywords.

[@gqntexas]

Great great explanation.. you always here that the differences is the 'block scope' and then wonder, well, like within an if or for loop, but nobody else ever says that...

[@dacfniel5442]

You are the best teacher on KZbin.

[@guillaumedupont2902]

This was SO helpful. Thank you so much!

[@B3ASTM0DE1]

This video came just in time. We are going through Javascript and JQuery right now in my bootcamp!

[@WebDevSimplified]

I'm really glad to hear. If you run into anything that confuses you in the bootcamp feel free to let me know, and I can try to help or make a video on the topic.

[@B3ASTM0DE1]

@@WebDevSimplified Awesome will do!

[@sagarioharvey6910]

Web dev here in the PH. "Man I love your videos, your making a great impact" //awesome

[@bujjivenkateshwarlu6942]

Hey thanks. earlier i had confusion about block scope and Function scope. Now its cleared.

[@nessparadis6948]

Great video. Succinct, clear to understand, and I learned a lot. Thank you.

[@videospromoter5884]

Checked 10s of video and this video told me hmm you understand this now . say thanks to him :) Thanks Dude

[@borislavaborisova7274]

Thank you! This video was very helpful. Just what I needed.

[@pooja6380]

learn so much important points and the actual difference ....thanks a lot

[@user-se6ct5zu2f]

huge thanks for the explanation, only you made it clear to me!

[@therealbrucewayne24]

Yes I did learn something thank you very much man it was hard for me to understand this but you explained it in like less than 10 minutes lol you have a good day too :)

[@ev_dash]

Your videos are helping me out alot! Thank you ❤

[@derrick3534]

man you are teaching the things that are not widely discussed which is why i am going to subscribe. You have a true gift of teaching in simple terms. i enjoy your channel, especially the tutorial on promises

[@WebDevSimplified]

Thank you! I try to cover the topics that I know confused me or other people I know, because those will be the most helpful for others.

[@aisana99]

thank you :D you shared more differences than my constructor in my Full-Stack Bootcamp! Will subscribe and watch all other videos of yours

[@baliyachtservices7505]

I was wondering just that! Thanks so much

[@sadhappy8860]

Super clear explanation, many thanks

[@michaelmaloy6378]

Whenever I see that face, I know useful information is coming my way. Simple, clear, and very helpful. Thank you as always!

[@derickbank1064]

Thank you for the explanation. Well explained. !

[@JonasGavenas]

Great lesson! Thank you, perfect explain.

[@wr1818]

thankyou for all the amazing explaining!

[@theNikijspictures]

Really good explanation, for beginner level - if reading info only in text (with no visual examples), it gets confusing quickly on this topic. Cheers😉

[@JEffinger]

Thank's bro that was a really clear explanation.

[@sandybathwater8385]

So simple, thank you so much! If I search for something and see your face in the results, I am saved. :)

[@kazeemalatishe3828]

Thanks a lot. You explain things really well.

[@oceanmind1793]

You made it so clear. Thanks a lot

[@injector6926]

Best Web Development I seen evrr

[@monireachtang712]

very clear explanation! you are awesome!

[@tiltify2393]

finally I understand the difference, thanks man A LOT

[@weligamage1]

Clear and concise, Thank you

[@hoakeen]

Awesome tutorials! Thank you!

[@NedumEze]

I love your approach so much. Thank you. I do have a fundamental problem though. Maybe you can consider making video of it. It is this: When I create an external JS file, and I have in it, codes like functions, etc in it, only the first code or function works! What should I do to ensure that different codes intended to fire at different Listeners, in the same file, work?

[@somtovitus]

Best video on this topic

[@coderbhai4832]

1)Declaration Let variable in a {} block scope can't be access outside of it 2)let name = value1, let name = value2, can't redeclare let twice Instead of this should be written name=value2; 3)let can be change it’s value const can't as it is constant but it can change its object value.🙃

[@chalk1007]

yeah, I was a little confused aswell but this video was made in 2018

[@dozadetrezire7455]

You forgot to say one more thing: when you declare a variable with var keyowrd, this automatically creates a property inside the Window ojbject.. so, if you say for example: var x = 1; and after that you say: console.log(window)... you will see that in the window object you will find the property X with the value of 1. Instead, if you declare a variable with let or const, this won't ceate a property inside the Window object. I guess this was also very important to mention!

[@shresthsrivastava27]

Awesome explanation !

[@pashashyba5006]

Quite easy to understand. Thanks

[@nobitalazy9791]

you are a rare gem my friend!!!

[@ihaseeb_khan]

Thank you bro, really helpful :)

[@khisus20]

This is truly simplified

[@priyanshugupta7614]

thank you your explanation was very clear

[@FredRosa]

Great tutorial, thanks!

[@mirzashowvik564]

Great video !!! Love it

[@user-yi4zd6gh5h]

great explanation. TY!

[@stuartgreen5217]

Been building sites for 30 years and always avoided JS due to pre jquery experience. Am now taking the time to relearn JS and node while I’m at it and I have to say I’m regretting not doing this sooner. I’ve been programming in C# php Perl VB and JS is a peace of cake by comparison .

[@mayorb37]

You make a wonderful work 👍👍👍👍👍 thanks

[@EyeIn_The_Sky]

Good old Java script, Let (no pun intended) us introduce "const" that does not allow for re-assigning to avoid human error so that it is "constant" except when it's not...

[@hanntongfong1226]

Great work! 👍

[@RS-nz6rn]

Thanks for clarifying.

[@jankiramulu]

Wonderful explanation.. Than you....

[@andreas-wismann]

Great! Suggested topic while you're at it: Semicolons in JS - use or omit?

[@letsgetto1millwithoutvids]

Good video finally understand and I could have used var for something I needed instead of saving it to local storage and grabbing it after 🤦‍♀️

[@sebnargeurbrok1374]

well explained, thanks!

[@jimilittle]

That was awesome. Thank you

[@tinpham6413]

Love your channel

[@kamalsyed4237]

loved it! Thanks.. Const, Let, Var .. it is :)

[@robertoriosmorales7528]

awesome explanation

[@andreastewart6133]

Helpful. Thank you.

[@namratadas5569]

Grt video... can you make videos on concepts such as closures,iffis,apply,call,bind methods...etc?

[@53strat55]

Solid video!

[@tomschwrs]

Great Video!

[@jahneychriast2141]

தெளிவான விழக்கம் நன்றி 🙏🏽

[@manojbharadwaj456]

That's so motivating. Because nobody understood that!

[@rajlakshmijoshi]

Thnks for the detailed vid, just one correction: At 5:35-> const does not allow to 're-declare' the variable, actually should be const does not allow to 're-assign' the variable, but let do.

[@vikasnigam9646]

Gr8 explanation.

[@johanledel1407]

Thank you!

[@vikumravinayake1882]

Problem solved Thank you very much. Ur a good explainer....

[@aadityakiran_s]

I came from C#. It's pretty simple there. Use var for what you wanna change, const for what you don't wanna change; variable and constant. Simple language for simple people.

[@andyarellano7474]

Thank you so much bro.

[@placeholder_name321]

so so simple. Finally.

[@xilliman]

im declaring every variable as const and then change it to let if i have to reassign them. this makes the code much safer. i don’t use var anymore

[@halofreak644]

You the real MVP

[@SumitSinghrao]

Could you also explain if we declare a variable without var, let and const? Could you also make video on 'this' keyword.

[@redpadweb]

Thank you so much.

[@agaming7888]

thanks for this now i know what to do 👍👍👍👍

[@surendergaini3365]

GOOD explaintion

[@NehaGupta-fd8hs]

Great Stuff!

[@WebDevSimplified]

Thank you!

[@ruslankovalov8292]

Thanks God we have you to explain this!! thanks!! A lot! A mean that)

[@khaktus]

While I prefer Kyle's tutorials over the others for various reasons (extent > clarity > simplicity), for this one I'll differ from the praise-storm below - this was just one of the many confusing explanation of the var|let|const topic that I've seen so far. This is the problem that many skilled developers have - they assume that as developers they have analytical thinking and provide well structured explanations (naturally, by default) - but I have seen - since the university times to professional days - that the paradoxical situation happens: techies often do the exact opposite: they do not adhere to the structure/hierarchy of the topic, nor the consistent use of terms they set in the beginning. :D Something to work on throughout professional life. In first part, you repeatedly state that var does and let does not allow to redeclare the variable, then you say the difference between let and const is that const does not allow to redeclare the variable. That paused my brain, while explanations went on. Maybe stating more clearly what is the difference between (your use of) "redeclare" and "redefine" and "reset" and "reassign" ... would help. Particularly in this one topic. :) I'd welcome more "technical" "analytical" (or tabular ;) ) than the "narrative" approach here. And particularly a consistent use of terms. 1 minute: redeclare: var|let|const myThingy = 10 var|let|const myThingy = 20 redefine/reassign/reset variable value: var|let|const myThingy = 10 myThingy=20 redefine object|array items value (not object|array value, which is just its memory address, so that remains "constant"): var|let|const myObject = [10, 11]; myObject[0] = 20 1 minute: | redeclare| reassign value of variable | reassign value of item in the array or property in the object| ------------------------------------------------------------------------------------------------------------------------------------------------------------ var yes yes yes let no yes yes const no no yes Also, from the many lessons on the scope, I understood that "scope" is something defining on what level of nesting we are (regardless if it is a function or block or just anything between {}). This perspective was often emphasized. Here, for the first time, I hear that different scope is actually defined by either function or block. Good point here!

[@nowhererealm]

dude yes! I was wondering how the heck are there so many people praising the explanation when i couldnt understand why he said let cant redefine a variable then goes on and says thats the only difference between const and let?? lmao wtf

[@RMNSH99]

Thanks Kyle

[@RakeshBitling]

can you please cover topic related to redis cache along with aws

[@koldwar4041]

Hi I always get a parsing error when I write const in my . Js file can you help me?