How Does React Tell a Class from a Function? • Hacker News Board

Re: How Does React Tell a Class from a Function?

#51

Post by ricardobeat » Mon, Dec 03, 2018, 7:27 AM UTC

sophiebits wrote: post #44

finchisko wrote: post #43

I'm pretty much aware about prototype inheritance in js. But still scratching my head everytime, I try to understand difference between prototype and __proto__. Thankfully with ES6 classes and class inheritance constructs, we don't need to override prototype constructor and such a things anymore. Still wish, that somebody will explain it to me in plain english.

This post does try to explain it in plain English. See the explanation starting at the bolded sentence that starts "Confusingly,".

Honestly I don’t think it does a good job at explaining it. Classes are mostly syntax sugar for “old” constructors and prototypes, not the other way around (that’s the whole reason you can’t tell them apart). Would be easier to explain it that way; on mobile right now so can’t comment too much.

Re: How Does React Tell a Class from a Function?

#52

Post by welfare » Mon, Dec 03, 2018, 7:40 AM UTC

ricardobeat wrote: post #49

“In the old days, JavaScript did not have classes” gave me a laugh. This was 3-4 years ago.

How I read it, "Old days" in my opinion refers to the 90's and early 00's, and not so much about the recent changes in the language.

Re: How Does React Tell a Class from a Function?

#53

Post by torgian » Mon, Dec 03, 2018, 7:53 AM UTC

Ugh. This just doesn’t make me want to touch JavaScript. I’d rather stick to Django and Python

Re: How Does React Tell a Class from a Function?

#54

Post by Kiro » Mon, Dec 03, 2018, 7:57 AM UTC

> In the old days, JavaScript did not have classes.

Feels like yesterday to me. I still do my objects prototype style because classes feel too new and bleeding edge.

Re: How Does React Tell a Class from a Function?

#55

Post by dakom » Mon, Dec 03, 2018, 8:05 AM UTC

reificator wrote: post #41

pests wrote: post #38

Earlier quoted context omitted.

I don't understand how "React/Vue/Angular" is considered "an entirely new language." I use React primarily, so I'm going to speak from knowledge of that. It is very obviously a framework and it does one thing - handle your view. Depending on what you are doing, you may have very little react-specific code in your application. You have data fetching, caching, persistence, authentication, tons of things, not to mention…

While I agree with your point, your example of React literally adds a DSL that requires a pre-compilation step. It's not required[0], I get that, but it's still a new language. [0]: It may not be required, but it was created for a reason....

JSX is not only not required, it's sugar that breaks referential transparency: https://medium.com/@david.chambers/jsx-violates-referential-...

Personally I still use it, but I think it's fair to say that as much as JSX was created for a reason, it's made optional for a reason too.

Re: How Does React Tell a Class from a Function?

#56

Post by sorahn » Mon, Dec 03, 2018, 8:07 AM UTC

alangpierce wrote: post #36

galaxyLogic wrote: post #31

You get an error if you try to call an ES6 class as a function (without 'new'). So just try to do that inside a try-catch. If there is no error you know it is not a class and you have the result of the function already. If you do get an error and you know it is a function you know it must be a class.

I believe throwing and catching exceptions over and over as part of normal rendering is the sort of thing that would be disastrous for performance, certainly the sort of thing that the React authors would really want to avoid.

The new suspense api is based on throwing and catching promises as part of the render, so I don’t think its that.

Re: How Does React Tell a Class from a Function?

#57

Post by pests » Mon, Dec 03, 2018, 8:26 AM UTC

sophiebits wrote: post #47

pests wrote: post #46

Earlier quoted context omitted.

I don't mind a pre-compilation step as I'm already doing it in my projects and a lot of the community is as well. There are other templating systems you can use in React if you don't like JSX. I've seen one codebase use direct calls to ReactDOM.createElement and there is a new hotness (which I can't think of the name of now) that replaces JSX with template literals, something like: function NamePetList(props) { retur…

You're likely thinking of https://github.com/developit/htm .

Oh yes! Thank you.

Re: How Does React Tell a Class from a Function?

#58

Post by yuchi » Mon, Dec 03, 2018, 8:30 AM UTC

jakelazaroff wrote: post #23

chrisweekly wrote: post #9

Earlier quoted context omitted.

Abramov's a class act all the way.

Or is he a function act?

:clap:

Re: How Does React Tell a Class from a Function?

#59

Post by miklax » Mon, Dec 03, 2018, 9:02 AM UTC

I like a domain name.

Re: How Does React Tell a Class from a Function?

#60

Post by arry » Mon, Dec 03, 2018, 9:13 AM UTC

What's the rationale for allowing the components to be defined as functions in the first place? As far as I can see, it has a single thing going for it: saving a line of code, at the expense of jumping through the JavaScript hoops to implement the class/function distinction described in the post. Besides, when the function component evolves and acquires the need for state or other features, the saved line of code goes right back in.