JavaScript Classes vs Prototypes

This tutorial discusses the differences in syntax between creating objects in javascript with the class keyword or with the prototype methods.
Examples are given of doing the exact same things with both versions.
It is important to understand that the class syntax is being interpreted as using the prototype syntax and that CLASSES do NOT exist in JavaScript.
Completed Code GIST: gist.github.com/prof3ssorSt3v...
Code Note: line 50 should be
Object.setPrototypeOf(EmployeeP.prototype, PersonP.prototype); //extends
We are setting the prototype of EmployeeP's prototype to link to the prototype of PersonP.

[@judaspriest33715]

I can probably count on one hand how many truly clear and straight forward youtube coding tutorials I've watched, this is one of em, hitting subscribe!

[@DRocksRecords]

Yeah each time I stumble on a video he made I feel like someone with confident knowledge is showing something useful. I subscribed too

[@IONYVDFC]

Great video! Being an old-school C++ developer, I personally never understood why JavaScript ever needed to borrow the class syntax. One cannot really deny anymore that classes exists in JavaScript, they surely didn't. I prefer the syntax 'prototype' above 'class'. Many early C++ book editors around 1990 had a hard time explaining what a class is all about, almost apologetic for the confusing word choice. A prototype really says what it does, as it shapes how the instantiated object will look like, while a class has nothing to do with classification.

[@NourHomsi]

I've been a Javascript programmer for more than 10 years, but suddenly, you opened my mind to a whole new sight to OOP in Javascript !!

[@machineshouldbe]

My head is still spinning, but this breakdown helped me understand how to use classes more. Thank you so much.

[@sahasrabhujaneuron5975]

This is exacly what I'm looking for! Now it makes more sense why the syntax in class is constructed in a bit of a weird way. Many thanks!

[@LR-bc8js]

I think in <a href="#" class="seekto" data-time="676">11:16</a>, the line should be Object.setPrototypeOf(EmployeeP.prototype, PersonP.prototype) instead. Great video! I love it!

[@SteveGriffith-Prof3ssorSt3v3]

Yes that line was changed in the description and in the code gist.

[@barungh]

"It is important to understand that the class syntax is being interpreted as using the prototype syntax and that CLASSES do NOT exist in JavaScript." Great 👍

[@manjoujanzen9375]

great way to explain, clear and in a not too fast speed, so the brain can follow. thank you for the great tutorial.

[@rotrose7531]

I never dreamed I can understand these class things, but after this tutorial, those abstract things go straight into my head without any resistance. legend teacher, as always thank you.

[@JeatBunkie]

So happy I found your channel, I could cry! You’re making every subject I was shaky on just make sense!

[@igoroliveira9146]

Steve, you are the ONLY ONE I found online, that explained well enough so I could understand, I always tried to find a relationship (a kind of "translation") between functions and classes and you simply explained it. Perfect video. Thank you very much.

[@LR-bc8js]

Same thing here bro :)

[@thippanayugesh8414]

this channel is pure gold.

[@ManjunathManja1227]

And so underrated.

[@Maru-ge6jn]

No bs, straight to the point, clear explanations with clear examples. So underrated!

[@adirbarak5256]

such a good tutorial, you don't skip anything and actually understanding what's a class doing and how to simulate it using prototype explains the logic behind it.

[@Claudia-hz4ly]

Omg! I finally understood prototypes - I have watched three different tutorials and I still did not get that...until I came across this video! Thank you so much!

[@josiahtobas9172]

Yooooo...been searching for a clear instructional video on this topic, finally found it. Thanks a lot.

[@p3k1n0]

After 10 videos on constructors, classes, and prototypes in javascript, finally a video that makes me really understand....thank you.

[@glenottley2823]

What a clear and insightful video on what can be a very complicated concept! I've saved your 'JavaScript from the start' playlist and will be working my way through, one per day. Thanks Steve for the great education!

[@abdouthiam7981]

This is so useful I cannot explain how much it made my learning prototype easy

[@marianofarace308]

I can't stress how clear this was. Thanks

[@TheLucidway]

Fantastic explanation. I can always count on this channel to clear things up. Thanks man.

[@jcoopsdrums8941]

Thank you so much, you have helped me sort out the details that were getting mixed up in my head.

[@jholtkort]

Thank you for creating this. Very good!

[@rongliao9255]

Great tutorial with super clear explanations! Thanks a lot!!

[@maniac5411]

Thanks for such clear, and concise concepts! Keep up the good work :)

[@arinamartens6858]

you are the best! you have nice voice and speech and so good at explaining, thank you

[@katdareshruti]

You truly deserve a Subscribe. Thank you for breaking down the complexities of a very confusing language!

[@manishmate9991]

The beeeeeeeeeeest explanation ever. Thank you so much mate.

[@kumargaurav4492]

Thank you! Steve, It's a great tutorial, and your explanation is really great. :-)

[@johnacsyen]

Very concise explanation. Better than code bootcamp. Subscribed

[@westonpetersring]

You are a true engineer, thanks man

[@michael.knight]

Excellent tutorial, thank you.

[@kranthikumar5215]

I have never seen a explanation like this really u r a great teacher sir applauds 🙏

[@muhammadhossam8557]

one of the best if not the best javascript channels in youtube

[@piegpa]

This is such a good explanation, thanks mate.

[@Cientificosdelsoftware]

Thank you man, you are very talented to explain those concepts... God bless you!

[@sergeyd9989]

Awesome. You made it clear for me, thank you.

[@sashaikevich]

Another clear explanation - thank you!

[@aaaaaab631]

Thank you so much. I am not good at english but your explanation is amazing. I can understand whole things. Thank you.

[@chesterxp508]

Another very cool tutorial!

[@B-Billy]

Prime level content!! You are really good at JS❤🎉

[@cmefindaname]

Gold! Incredible! Thank you!

[@JoseRios-yr6pc]

Thanks a lot! It's much clear now the concept to me

[@cuberos7430]

wuauu !!! You made it very easy . A lot of thanks, Blessings

[@meirunassmitas8762]

Clear and useful tutorial

[@aniketbharsakale2561]

Nice content, nice explanation, I'm a newbie & I could derive a lot of sense out of this. Helpful & v.much to the point. Clean clear crisp. And your voice is so cool :p Cheers keep this great work going.

[@kuldeeps1ngh]

Great explanation on JS classes. Thanks Steve.

[@SteveGriffith-Prof3ssorSt3v3]

I have a new video about classes too - kzbin.info/www/bejne/qqKlgWiQjZ15ZsU

[@jayant6172]

thanks for this video man. It really helped a lot.

[@ptk252]

VERY NICE..... Easy to understand.

[@pinakim11]

Thank you so much, you explained it really well.

[@mpc79]

Very well explained. I will be hitting subscribe.

[@AdrianJDeNiz]

Great video very helpful!

[@joesden9628]

Spiegazione eccellente, complimenti!

[@federicoprat9093]

my god finally i understand the difference, Thank you man you saved me.

[@gautamjiart]

Really good explanation

[@chamonroy8453]

Loved it, pal.

[@TuTrinh211]

Great explanation!!!

[@memoriesalivee]

Great explanation. Thanks :)

[@Pareshbpatel]

JavaScript Classes and Protototypes beautifully explained. Thanks, Steve {2023-08-18}

[@ahmedelgaidi]

thank you it' s a really good one

[@Richard.halabi]

thanks Steve very helpful.

[@mohammadshoaib5881]

great video man. Thanks

[@herrbasan]

Just discovered your channel, man .. if only you've been around 20 years earlier, I would be a JS master by now :) The thing that confused me for many years is what "this" means depending on the different contexts. I was a AS3 developer for many years, so i was used to the class logic, never understood the "prototype" concept because of that. When "class" was introduced in ES i finally could work the way i was used to. But thats why i've never understood "this". Now, i even think the prototype way of doing things is more logical. And understanding it clears up a ton of other things in JS that puzzled me.

[@SteveGriffith-Prof3ssorSt3v3]

Glad I could help. I loved teaching AS3 in Flash. Having the visual part made it so much easier to explain the Class concept. I did a video recently on "this" - kzbin.info/www/bejne/m4iniZqpfsyHfc0

[@anupammaurya6624]

Nice explanation 👍

[@JT-mr3db]

A lot of libraries use the manual prototype method and there are some neat tricks you can do with it. I first saw this when analysing mongoose code. There are some challenges if you want to represent this with types in a typescript project, I found using class syntax to be less pain in that regard.

[@SteveGriffith-Prof3ssorSt3v3]

I definitely have things that I do with prototype and then there are some cases - Web Components, extending Events, extending Errors where I will use the class syntax.

[@MannyGonzalezReyna]

Thank you professor.

[@karthickchandiran2397]

Nice tutorial

[@russellabraham9208]

Yea one of the nice things about class is its inheritance of scope. Thanks

[@belhadjersamir5413]

thank you very much ,you are great

[@aminehaine3301]

very clear, thank's

[@masaakistephanebenon547]

very helpful thanks a lot

[@hanenezribi4029]

Grenat tutorial , thanks you

[@ShivamMishra-mn6cs]

best explanation

[@everyhandletaken]

I was struggling with 2 things, what a class really is (in JS) & what practical purpose it serves for the work I do. You have answered that perfectly .. knowing that the class syntax is just syntactic sugar for functions makes my brain happy! Subscribed.

[@faarez_official]

Thanks man!

[@maksmephi]

Thanks, it is very helpfull)

[@sidarjunful]

After making a connection between the EmployeeP object and the prototype of the PersonP using Object.setPrototypeOf() method, a new prototype method(function) is added on the the EmployeeP object (in the line number 51) with the name of employeeInfo. So, my question is that whether this new method (employeeInfo) will be added to the prototype of PersonP or another prototype object of the EmployeeP? BTW your way of imparting the information (idea) is unmatchable, it's GOLD STANDARD. I will try to teach my students your way.

[@SteveGriffith-Prof3ssorSt3v3]

The new method on line 51 is only being added to the prototype of EmployeeP. With setPrototypeOf on line 50 we are explaining what the next step in the prototype chain will be. If some method is not found inside EmployeeP.prototype then JS will look inside PersonP.prototype. This video also helps my students - kzbin.info/www/bejne/ZmLNh5p5gJJ7jpY

[@arashvincent8519]

immeditly subscribed

[@islombekhasanov]

Perfection

[@DRocksRecords]

Thanks it made it clear to me that even if it ends up being the same thing, classes makes it more clear that they are tied together. I do wonder if one way performs better than the other tho but its probably not that important.

[@SteveGriffith-Prof3ssorSt3v3]

There's no performance difference because both syntaxes create the same objects with the same prototypes

[@alex-desroches]

@@SteveGriffith-Prof3ssorSt3v3 nice ok thanks for the reply, have a good day

[@choppinbrixx4931]

@@SteveGriffith-Prof3ssorSt3v3 Hi, Steve. Loved the video, thank you. I came here with a burning question that perhaps flew over my head. If they're doing the same thing, then what's the point of the redundant syntax and why chose one syntax over of the other?

[@lookupverazhou8599]

@@choppinbrixx4931 Trying to make it more declarative. That's what I got out of it anyway.

[@Snoo29293]

At <a href="#" class="seekto" data-time="673">11:13</a>, if you set the prototype of EmployeeP to PersonP.prototype, the EmployeeP.__proto__ becomes the PersonP.prototype, and the EmployeeP.prototype stays the same it was, that's what happens for me at least. Because of that the methods inside PersonP.prototype cannot be called through the objects created by EmployeeP. I don't know if I did something wrong, but to fix that I simply wrote Object.setPrototypeOf(EmployeeP.prototype, PersonP.prototype), so now the prototype object of EmployeeP function is a child of the prototype object of PersonP function, I think that's how the prototype chain for classes is too.

[@kranthikumar5215]

awaome man ❤

[@hcgaron]

Hi Steve, thanks for this video. I came back to this again after refactoring some code into factory functions and away from classes. My question is: with what you've shown here, will we still encounter the various pitfalls with 'this'? (ie. having to bind explicitly when invoked from another function -- my intuition says yes because this illustrates an alternate syntax for the same end result). To that end, would you recommend a more functional / composition based approach where factory functions return objects with certain properties and then object types are returned by composing those functions? Cheers!

[@SteveGriffith-Prof3ssorSt3v3]

With JS I would definitely recommend using a functional / composition approach to building things. Classes in JS are not what you expect from "class" in other languages. It is a nice clean syntax if you are building objects that will have a limited scope and interactions with other object types. However, when architecting anything in JS you need to think in terms of prototypes and composition works better there.

Great Steve. Cristal clear and you make it easy. But, what happens if you create a variable without new (i.e: let Jose = PersonP)?

[@SteveGriffith-Prof3ssorSt3v3]

Without the keyword new, any function returns whatever is written after the first return keyword in that function. If the function has no return statement then it returns undefined.

[@SinaGilassi]

Awesome video! I have a question regarding the number of functions that can be extended. For instance, EmployeeP extends PersoneP1 and PersoneP2.

[@SteveGriffith-Prof3ssorSt3v3]

You can create a prototype chain that is any length that you need. However, each object's constructor function can only have one prototype. The prototype will be one step in the prototype chain. If you are asking about combining the properties and methods of a bunch of different objects into a single new object, then you are talking about composition instead of inheritance. kzbin.info/www/bejne/nJPTiYRmmp2Appo

[@gayathrisathyan3892]

@steve griffith : Hello Steve. This is really Awesome. By far the best Explanation ever. All your Videos are Awesome. Keep Rocking. A Small Clarification, I feel it has to be Object.setPrototypeOf(EmployeeP.prototype, PersonP.prototype). [ You have written EmployeeP. This causes an error and I'm not able to call getDetails Function from the Base Class. ] Please do correct me if I'm wrong. Thanks

[@SteveGriffith-Prof3ssorSt3v3]

Yeah. I fixed that in my code sample afterwards. I also have a new video that I did to visually explain prototypes - kzbin.info/www/bejne/ZmLNh5p5gJJ7jpY

[@gayathrisathyan3892]

Steve Griffith Awesome Man. Thanks

[@bhagabatsahoo3112]

super

[@bulldawg4498]

As an advanced novice JS coder, I always found 'prototypes' confusing ... Your video makes the case for the class paradigm vice prototype model in my view ... Coming from the Java and Python world, classes and subclasses are the way to go and are more OOP than 'prototypes' ...

[@SteveGriffith-Prof3ssorSt3v3]

They both do the same thing internally. Both syntaxes are working with prototypes. The Class syntax was partly added to make the transition easier for people coming from languages like Java. Partly it was yet another attempt at trying to simplify something that has been a confusing mess for 20 years.

[@rizud5122]

Hi Steve, I am just starting my career in coding and have to say you are like a god of coding for me. I read blogs, excerpts from books, and what not but the way you explain things is just amazing. I am preparing for the MCSA-70-480 exam as a part of my apprenticeship and these tutorials are so helpful for a beginner like me. Just wanted to know if by any chance do you take personal coding classes or any sort of official coding lessons if somebody is interested in learning from you 1-1? My learning at this point in time is exam based and there are so many things that I come across in practice questions that I just can't understand and hence feel the need for proper mentoring for expedited learning.

[@SteveGriffith-Prof3ssorSt3v3]

I teach students, but only in my program at Algonquin College - www.algonquincollege.com/mediaanddesign/program/mobile-application-design-and-development/ I don't do mentoring or one-on-one tutoring. Just no time for it.

[@rizud5122]

@@SteveGriffith-Prof3ssorSt3v3 Yes, I understand. Wish I had a teacher like yourselves in my uni, your students are so lucky :-)

[@seanlynch1841]

This is fantastic. Are there any advantages of one over the other? Maybe private #variables in classes, for example?

[@SteveGriffith-Prof3ssorSt3v3]

It's just two different syntaxes for the same thing. Real #private variables are available in classes but you can mimic them with proper scoping and prototypes.

[@KeplerEmeritus]

Thank you so much for the very concise information. Sometimes I see projects on Github mixing these techniques (Especially Node.js projects). Why is that? Is there some advantage to mixing these or using one or the other?

[@SteveGriffith-Prof3ssorSt3v3]

Classes are just syntactic sugar for prototypes. In the latest updates to classes there are a couple unique things. But for the most part it is a developer preference on how to write the code. Sometimes it will depend on what else they are doing in the code and if it is more functional or more object oriented.

[@KeplerEmeritus]

@@SteveGriffith-Prof3ssorSt3v3 Understood! Thanks so much.

[@FozIrenics]

How many times have I watched this video over the last few months? Lost count...

[@Talhaguy]

Awesome explanation! Now I'm wondering if having the "class" keyword in JS makes things more confusing.

[@SteveGriffith-Prof3ssorSt3v3]

In some ways it does. But if you understand how the prototype system works then you just need to learn how the class keyword works with this. Just don't try to force your understanding of `class` from other languages into JS.

[@nicolascondrea8068]

Thanks

[@SteveGriffith-Prof3ssorSt3v3]

Thank you very much!

[@tolstoievski4926]

I'm still confused between prototype and the hidden property [[Prototype]] that os called by the accessor function __proto__ ?

[@SteveGriffith-Prof3ssorSt3v3]

There are 3 parts to this. 1. The object. 2. The constructor function that made the object. 3. The prototype object. The function (2) can access the prototype object with the `.prototype` keyword. The object (1) can access the prototype object with the dunder-proto keyword. Here is another video I did on the topic - kzbin.info/www/bejne/ZmLNh5p5gJJ7jpY

[@maitran1764]

At line 47 PersonP.call(this, nm, id) is there any other way to write it using the setPrototypeOf or Object create method? Thank you very much for your tutorial. Amazing as always!

[@SteveGriffith-Prof3ssorSt3v3]

We need to call the PersonP constructor to give us the name and id properties and their values. setPrototypeOf is just creating the prototype chain for inheritance. It is like calling super( ) inside the Class syntax's constructor( ) method.

[@josbellquiros7055]

Why do you need line 50? Where you set prototype? It seems that you can have inheritance just with the PersonP.call line. I imagine I'm missing some inheritance functionality that would be missing but I can't think of it.

[@SteveGriffith-Prof3ssorSt3v3]

There is a note in the description about a change on line 50. The code was changed in the repo too.

[@longingbydesign]

From what I'm reading, the use of Object.setPrototypeOf() is highly discouraged due to massive performance issues. I also miss how this relates to __proto__ in this very example. Last thing I noticed is that doing SuperClass.call(this, params) is called constructor theft in Nicholas Zakas' excellent book "Principles of object-oriented Javascript", and I wonder if there's any alternatives to that.

[@SteveGriffith-Prof3ssorSt3v3]

Yes. Use Object assign or with the class syntax you can use extends

[@0000SubZero0000]

Hey Steve, thanks for the great video. Can you tell me where to call Object.setPrototypeOf in order to apply the inheritance?

[@SteveGriffith-Prof3ssorSt3v3]

I'm showing how to use setPrototypeOf in the video. That is creating the prototypical inheritance. You can also use Object.create( ) or Object.assign( ) to denote a prototype. If you are talking about with the Class syntax, you can do it the same way. The Class is just syntactic sugar. It is a wrapper around the prototype system. You can add the keyword extends to a class OR you can use Object.setPrototypeOf or Object.assign to point to the prototype.

[@victorwong2270]

​@@SteveGriffith-Prof3ssorSt3v3 Love your videos. This line didn't work "Object.setPrototypeOf(EmployeeP, PersonP.prototype) " @ 11:20 . It doesn't seems to inherit its parent's method. Could you explain it please? Thx! Here is my codepen: codepen.io/victorw999/pen/KKzZMME

[@SteveGriffith-Prof3ssorSt3v3]

@@victorwong2270 There is a note in the description and in the code Gist that fixes that typo.

[@mac8911]

@@SteveGriffith-Prof3ssorSt3v3 Thanks for staying active in the comments. I had the same question. Didn't think to look in the description.

[@fifilulu]

Hi, great and clear video, thank you. What is the best option in pratice, classes or closures? Which offers the best performance?

[@SteveGriffith-Prof3ssorSt3v3]

In JS, classes and closures are two different things. closures in JS are a built-in feature that allows you to maintain reference to a value that would otherwise have been lost, so that you can use it at a later time. Closures will be used both with objects and prototypes as well as with simple functions and loops. JS classes are a syntactic sugar that lets you define/create Objects and their prototypes with a simplified syntax. As far as performance between classes and older Object.create syntax, there is no real difference. They both create a JS object and a prototype.

[@fifilulu]

@@SteveGriffith-Prof3ssorSt3v3 Thank you for the answer. Sorry, you are right, my question was between classes or prototypes.

[@SteveGriffith-Prof3ssorSt3v3]

@@fifilulu ok. Well the answer is the same. Classes are just syntactic sugar. They create the exact same prototypes behind the scenes . No difference in performance because they are the same thing

[@fifilulu]

@@SteveGriffith-Prof3ssorSt3v3 Interesting, I noticed that most experienced JS developers prefer prototypes. I concluded it was faster, but it is probably because classes have been lately added to the language.

[@SteveGriffith-Prof3ssorSt3v3]

@@fifilulu you will see a lot more of the class syntax when working with React developers. More experienced developers will be more likely to use the older syntax, like you said the class syntax is newer