Factory Functions in JavaScript

hello function years today we are talking about factories factories are simply functions that create objects and return them in most cases you can use factories instead of classes and factories are much simpler and less convoluted than classes are this is a weekly show where we try to become more confident and excited about programming by learning intriguing things that we didn't know before pre-requisite in order to understand this video you need to be familiar with closures if you're not completely sure what closures are you should watch the previous episode on that topic first before I show you a factory function I want to show you a class this is a dog class it does some setup in the constructor assigns a property to itself called sound the class also has a method talk which uses that sound we then instantiate at all say foods which we then call talk on and sniffles promptly tells us what this is fine but there are a couple of annoying things with classes if we assign the top method to something like click handler here things will break because now the this keyword inside the top method here will not be sniffles this is going to refer to something else in this case I think it's going to be the Dom element or something that it's not important exactly what but what is important is that it isn't going to refer to sniffles like you would intuitively expect to work around this you can use bind to force this to be sniffles this is a very common thing to do but it hurts my gentle and beautiful soul to look at this code it looks like cold blue another way of dealing with this problem is to wrap the top call in a function like this that looks better but it annoys me that I have to remember to do this at all to me it feels like a stupid trap in a shitty computer game in fact I think that the concept of this and new in JavaScript feels like that in general new and this are some kind of unintuitive weird clown rainbow trap that you just trip over all the time and I am so ashamed of it every time I introduce people to JavaScript but there is hope because in JavaScript you don't have to do classes in Java or C sharp and some other languages you have to use classes that's the way of instantiating objects but in JavaScript you have a bit more freedom so maybe we can try some other way enter factory functions here is our dog re-written as a factory function now dog is simply a function in it we create a variable sum and we assign the value woof to it we then return a simple object literal with one property Tork a function which logs out the value of sum and because of the awesomeness of closures top has access to the variable sound a bonus feature here is that the code outside of the Dom doesn't have access to the sound variable so the sound variable is actually properly private to the dog which it isn't in the class I notice here that we are not using that this keyword at all and because of that the reference to the sound variable will always be correct even when we use class in the way that broke in the class example like this I think that for almost all cases you will be better off using factories for other than classes because your code will be simpler and easier to reason about there is one case where I think it's not like to use classes and that is if you find yourself in a situation where you need to create a lot of objects it cause classes have a bit better performance but note here when I say a lot I mean a lot instantiating an object on my computer using a factory takes zero point zero point zero point zero point four milliseconds using a class is twice as fast actually 0.0.0.0 hmm point two milliseconds if you do the math this means that if you're creating say 10,000 instances using classes over factories will earn you a directed a to milliseconds so if you're creating just a couple of hundred or even a couple of thousand items per frame the performance difference between a factory and class is not going to matter to you if you are creating more than 10,000 instances per frame then classes might be for you but you should really ask yourself if the problem isn't that you're creating 10,000 items per frame in the first place in summary factories or simply functions that create and return objects we looked at a simple example of how you can use a factory instead of a class and how the factory is less convoluted than a class we also talked about how classes are a bit faster but that it is by so little that it only matters if you're creating at ten thousand items per frame or more do you have thoughts or questions maybe you even disagree good post a youtube comment down below and me or a fellow viewers I'll respond to your inquiry again in this show we try to become more excited and confidence about programming I'm learning intriguing things that we didn't know before new episodes every Monday morning so make sure that you don't miss the next episode subscribe to the channel here on YouTube or follow me on Twitter at mvj week until next Monday stay curious you

Channel: Fun Fun Function

Views: 187,015

Rating: 4.9446111 out of 5

Keywords: JavaScript (Programming Language), factory function, Software Development (Industry), Software Developer (Project Role), Software (Industry), Software Engineering (Industry), Programming Language (Software Genre), Software Design Pattern (Field Of Study)

Id: ImwrezYhw4w

Length: 6min 34sec (394 seconds)

Published: Mon Sep 14 2015