It would be nice to see a list of reasons one might choose this over angular or any of the other frameworks. The features and description on the homepage are pretty vague...
Apparently, you don't use this instead of another framework, but with (http://facebook.github.io/react/docs/common-questions.html).
To me, the closest existing thing to this would be Coffeescript as both need to be compiled into plain Javascript.
Okay, so I can use it with other libraries. But they haven't told me why I would. What problems, eg, is it solving that angular is not, or in a better way than angular does?
React is designed for building big UIs. The type where you have lots of reusable components that are handling events and presenting and changing some backend data.
In a traditional MVC app, React fulfills the role of the view (and maybe the controller, depending on your definition).
React's technique is to break your view down into smaller, composable components. These components provide a render() method which specifies how the component will generate its markup. render() can either return normal DOM elements (like <div>s) or can return other components.
When your data changes, the render() method is called again. We compare the old render()'d version with the new one and the framework determines the most efficient way to update the DOM. Often this will be faster than hand-coding it, as React knows about the entire state of the page and can do cool tricks like batching reads and writes.
The way we're able to pull this off is by constructing a very fast, lightweight representation of the DOM which knows which parts are dirtied and which parts are clean.
Because this rerender is so fast (on the order of 1ms for TodoMVC), we don't need the end user to explicitly specify data bindings. We've found that this is an easy way to build apps.
Wow, OK. This could definitely do with being included in the introduction - my first impression was "calling render() all the time and rebuilding the chunk of HTML must result in terrible performance on mobile devices etc". Your explanation here makes the whole system make a ton more sense.
Thanks for answering. It's nice to know the technical details, and I feel like you partially answered my question, but I'm still not 100% clear on the advantages over angular. What I gathered from your answer is that 2 advantages are:
1. It's faster than angular. Perhaps able to handle larger applications with tons of things going on better? But how large is large? I want to see an example app that React handles easily and angular struggles with. I know the Todo App example is mandatory, but angular (and every other framework) handles those well already.
2. It's perhaps easier to code and maintain than angular. I'm guessing this from your comment about data-bindings being unnecessary. But I'm not totally clear, as data-binding and updates are automatic in angular.
I know there are politics involved when comparing yourself to a competitor, and most programmers seem to be overly respectful of their peers, which I can appreciate. But it's too easy to fall back on the party lines "X and Y solve different problems", "X and Y have different strengths", and "You should try both out and decide for yourself!" As a framework user, these kinds of niceties are unhelpful and frustrating. It shouldn't be considered rude or disrespectful to factually list the advantages of your framework over the obvious alternatives. It is, after all, the only thing I'm really interested in as a user.
So my suggestions would be:
A bullet point list of advantages of this framework over angular, being as clear and specific as possible.
If they're good for different situations, I want to know what those situations are.
A big showcase app with the tons of components you alluded to, all working in beautiful harmony. I should be able to click a link to see the demo, not have to pull from github. And ideally there would be some accompanying walkthrough showing code snippets for various parts of the app, and explaining why they are so awesome.
React's technique is to break your view down into smaller, composable components. These components provide a render() method which specifies how the component will generate its markup. render() can either return normal DOM elements (like <div>s) or can return other components.
When your data changes, the render() method is called again. We compare the old render()'d version with the new one and the framework determines the most efficient way to update the DOM. Often this will be faster than hand-coding it, as React knows about the entire state of the page and can do cool tricks like batching reads and writes.
The way we're able to pull this off is by constructing a very fast, lightweight representation of the DOM which knows which parts are dirtied and which parts are clean.
This describes angular, that's what angular does. Edit: Well it's similar to what angular does, the intent is the same, but it doesn't know the state of the DOM among other things.
Because this rerender is so fast (on the order of 1ms for TodoMVC), we don't need the end user to explicitly specify data bindings. We've found that this is an easy way to build apps.
Angular's got a lot of great ideas, but the key difference is how you build with React.
Angular's directives are pretty similar conceptually to React components, yes. But Angular requires you to imperatively manipulate the DOM in its linking functions, whereas with React you declaratively specify how you want your component to look and when it changes state the framework computes the fastest DOM manipulations for you, which we think saves you some work and is often more performant.
If I had thorough benchmarks available I'd provide them, but sadly benchmarking things correctly is a lot of work and I just don't have time :/ You could try to play around with both frameworks' TodoMVC examples with Chrome's devtools to compare them, though.
Angular douesn't require you to use linking functions. They aren't necessary for 90% of the time when you can just use a template and a controller. It would be interesting if you provided an example in React of something that did require a linking function in Angular.
I wish we had some bigger examples checked into the repo. I'll work on fixing that. A few things:
- We've built lots of big components on Facebook and all of Instagram.com with it. Those are pretty big apps (though I know, you're asking for code and want proof).
- I think that composing UIs with JavaScript and components is easier than using directives or a templating language. For example, because Angular uses ng-repeat to construct lists, if you want alternating row colors you use something like ng-class-even. I think that creating a new directive for every use case is less intuitive than how you'd do it in React:
We could be more flexible than that. Let's say we wanted to, for some reason capitalize every other row. With Angular we'd need to create a new directive, with React it's just:
If is as fast as described, it's a godsend to Backbone developers. I love Backbone, but as I described below, I've ended up learning AngularJS because handling the DOM can be so tricky and cumbersome when you use Backbone.
And AngularJS is a great project that definitely solves most performance issues, but as you pointed out, many facets of directives are pretty unintuitive. And integrating third-party libraries is a pain with AngularJS.
So I'm really excited about trying this out. I really like the sample you put on pastebin -- very intuitive for Backbone devs.
thanks for the examples. it actually seems analogous to angular. the "createClass" bit is like a directive definition, and the "renderComponent" bit is like your new declarative markup. i do agree that angular can be complex and opaque, especially once you start to delve into the internals (compiling, priority, transclusion, etc), and avoiding that complexity is a good selling point. if i were you, i would hit that hard :)
that said, those examples don't seem all that different to me than the angular way. maybe the simplicity would start to shine in more complex use cases. again, a good toy problem that requires angular gymnastics to solve, side by side with a straightforward react version would be compelling.
my final and important question is this: you mentioned react only solves the view problem. does that mean if i want to migrate from angular to react that i would have move from angular to "react + backbone" or "react + something else"?
For Instagram we have higher level components that do data fetching via a JSON GET request. When the request comes back we store the response in state, and then we pass that state down to child components. We also pass callbacks down to those child components, so that when they want to perform a write to the server, the higher level component can do that.
We move the actual server request and response logic out of the component, of course, so it's just a one-liner within that component.
Instagram got really far with that, but there are parts of Instagram (converted from an earlier Backbone version) that have the child components directly update Backbone models which then handle the server requests. The on change Backbone events then trigger setState() calls on our UI.
At Facebook we have an in-house dataflow architecture that updates our components.
So it really depends on how you want to do it. But we don't provide a "React.Data" or "React.Router" or anything like that. This is by design, since we can't possibly account for everyone's specific use case.
I like the idea of being able to use my own raw domain objects as the model, which in angular you are supposed to wrap up as a service as i understand it -- a bit of boilerplate i don't love. I'll definitely keep my eye on this project, it sounds like it has a nice architecture.
My last piece of advice is docs, docs, docs. Making a framework easy to learn by example is the key to adoption imo. That was one of the chief complaints you heard about ember, though I think they've started to fix that. It's boring work and hard to make good docs, but it's so so important.
> I like the idea of being able to use my own raw domain objects as the model, which in angular you are supposed to wrap up as a service as i understand it -- a bit of boilerplate i don't love.
This is only a cultural thing. Angular is, at its root, a dependency injection framework. The upside of doing thinngs the angular way is that you can wire things together differently down the line (and you can actually get a lot of code reuse if you write 1-2 function services) with the downside being the boilerplate wrappers.
Thanks for taking the time to follow this conversation through :) We've spent a lot of time getting the docs to where they are today, but there's always more to do. We have more planned but think we got a pretty good point for our initial public release.
When we've showed the site internally at FB & Instagram we got a lot of the same feedback you're giving now, that we need more examples. We have some more in the repo and more we'd like to write. Coming soon!
Some things after I've been working with it for a few months
1) One of the great thing of React to me is the fact that we're writing everything in Javascript. With a very small syntax enhancer that is JSX you can write XML inside of the Javascript.
The end result is that you don't need to learn a template language or many new concepts such as all the ng-repeat, or code inside of strings that angular has.
If the framework doesn't support something, you can just implement it yourself. The React dom nodes are just regular javascript objects and you use regular arrays to manipulate them.
It is also very convenient to be able to write XML in Javascript. You work with html trees all the time yet you can't easily make new ones in js.
2) Having a representation of the DOM in javascript is a huge enabler.
Out of the box we can batch all the expensive DOM operations and only update the parts that actually changed.
But it allows to do more crazy things. We can put all our application logic in a web worker or render the page server side. There are a lot of cool possibilities once you are in a React world.
3) One of the huge issue we face as js developer is traversing the dom to get a reference to whatever node we want. jQuery shine with that. React transforms the paradigm. Instead of finding dom nodes you are creating them.
It leads to different ways of seeing the world. If you want to hide an element, instead of finding it and hiding it, you just don't create it in the first place.
This is great. To be frank, if I knew this was in the pipeline, I wouldn't have spent the past few months learning AngularJS. AngularJS, but it's fairly unintuitive to learn, and working with 3rd party libraries can be a pain with AngularJS. Most importantly, I already had a good grasp of Backbone. I love how Backbone organizes apps, and I love consuming REST APIs with Backbone. But handling the DOM is a pain in Backbone, and can result in performance issues if you're not careful.
This project appears to solve this issue and to integrate well with Backbone. I'm really looking forward to learning more about React.js.
Curious about this one (coming from mobile web perspective crappy cpu, high latency).
Render the page with node / serve html / React calls its render functions? / something else ? How does it bind to the already existing dom without building it? do all the render()s have to be called twice (once on server, once on client)?
Hey, I built this feature and was super stoked about it :)
First of all, we haven't released the official server rendering stuff yet, since the API still needs to be cleaned up. But it's a total of 20 lines or so, so I'll likely post an example soon :)
So React has a very low degree of coupling to the browser. Specifically it has two phases:
1. Generate the HTML markup, giving each DOM node a unique ID
2. Attach top-level event handlers. When an event fires we look at the target ID to figure out which component to bubble to (we have normalized, cross-browser bubbling and capturing built into our synthetic event system).
In client-rendered apps we run both of these on the client. For server rendered apps, we initialize and only generate markup on the server and send it down. Then on the client we re-initialize, but notice that the markup is there so we just attach event handlers.
This system enabled us to build a prototype a while back that ran React entirely in a web worker, but we haven't had time to productionize that yet.
