Since its 2013 release, React has supported all popular browsers, including Internet Explorer 8 and above. We handle normalizing many quirks present in old browser versions, including event system differences, so that your app code doesn't have to worry about most browser bugs.
Today, Microsoft [discontinued support for older versions of IE](https://www.microsoft.com/en-us/WindowsForBusiness/End-of-IE-support). Starting with React v15, we're discontinuing React DOM's support for IE 8. We've heard that most React DOM apps already don't support old versions of Internet Explorer, so this shouldn't affect many people. This change will help us develop faster and make React DOM even better. (We won't actively remove IE 8–related code quite yet, but we will deprioritize new bugs that are reported. If you need to support IE 8 we recommend you stay on React v0.14.)
React DOM will continue to support IE 9 and above for the foreseeable future.
With React you simply pass your event handler as a camelCased prop similar to how you'd do it in normal HTML. React ensures that all events behave identically in IE8 and above by implementing a synthetic event system. That is, React knows how to bubble and capture events according to the spec, and the events passed to your event handler are guaranteed to be consistent with [the W3C spec](http://www.w3.org/TR/DOM-Level-3-Events/), regardless of which browser you're using.
With React you simply pass your event handler as a camelCased prop similar to how you'd do it in normal HTML. React ensures that all events behave similarly in all browsers by implementing a synthetic event system. That is, React knows how to bubble and capture events according to the spec, and the events passed to your event handler are guaranteed to be consistent with [the W3C spec](http://www.w3.org/TR/DOM-Level-3-Events/), regardless of which browser you're using.
## Under the Hood: Autobinding and Event Delegation
@ -12,7 +12,7 @@ React provides powerful abstractions that free you from touching the DOM directl
React is very fast because it never talks to the DOM directly. React maintains a fast in-memory representation of the DOM. `render()` methods actually return a *description* of the DOM, and React can compare this description with the in-memory representation to compute the fastest way to update the browser.
Additionally, React implements a full synthetic event system such that all event objects are guaranteed to conform to the W3C spec despite browser quirks, and everything bubbles consistently and efficiently across browsers. You can even use some HTML5 events in IE8!
Additionally, React implements a full synthetic event system such that all event objects are guaranteed to conform to the W3C spec despite browser quirks, and everything bubbles consistently and efficiently across browsers. You can even use some HTML5 events in older browsers that don't ordinarily support them!
Most of the time you should stay within React's "faked browser" world since it's more performant and easier to reason about. However, sometimes you simply need to access the underlying API, perhaps to work with a third-party library like a jQuery plugin. React provides escape hatches for you to use the underlying DOM API directly.
@ -53,45 +53,8 @@ _Mounted_ composite components also support the following method:
* `component.forceUpdate()` can be invoked on any mounted component when you know that some deeper aspect of the component's state has changed without using `this.setState()`.
## Browser Support and Polyfills
## Browser Support
At Facebook, we support older browsers, including IE8. We've had polyfills in place for a long time to allow us to write forward-thinking JS. This means we don't have a bunch of hacks scattered throughout our codebase and we can still expect our code to "just work". For example, instead of seeing `+new Date()`, we can just write `Date.now()`. Since the open source React is the same as what we use internally, we've carried over this philosophy of using forward thinking JS.
React supports most popular browsers, including Internet Explorer 9 and above.
In addition to that philosophy, we've also taken the stance that we, as authors of a JS library, should not be shipping polyfills as a part of our library. If every library did this, there's a good chance you'd be sending down the same polyfill multiple times, which could be a sizable chunk of dead code. If your product needs to support older browsers, chances are you're already using something like [es5-shim](https://github.com/es-shims/es5-shim).
### Polyfills Needed to Support Older Browsers
`es5-shim.js` from [kriskowal's es5-shim](https://github.com/es-shims/es5-shim) provides the following that React needs:
* `Array.isArray`
* `Array.prototype.every`
* `Array.prototype.forEach`
* `Array.prototype.indexOf`
* `Array.prototype.map`
* `Date.now`
* `Function.prototype.bind`
* `Object.keys`
* `String.prototype.split`
* `String.prototype.trim`
`es5-sham.js`, also from [kriskowal's es5-shim](https://github.com/es-shims/es5-shim), provides the following that React needs:
* `Object.create`
* `Object.freeze`
The unminified build of React needs the following from [paulmillr's console-polyfill](https://github.com/paulmillr/console-polyfill).
* `console.*`
When using HTML5 elements in IE8 including `<section>`, `<article>`, `<nav>`, `<header>`, and `<footer>`, it's also necessary to include [html5shiv](https://github.com/aFarkas/html5shiv) or a similar script.
### Cross-browser Issues
Although React is pretty good at abstracting browser differences, some browsers are limited or present quirky behaviors that we couldn't find a workaround for.
#### onScroll event on IE8
On IE8 the `onScroll` event doesn't bubble and IE8 doesn't have an API to define handlers to the capturing phase of an event, meaning there is no way for React to listen to these events.
Currently a handler to this event is ignored on IE8.
See the [onScroll doesn't work in IE8](https://github.com/facebook/react/issues/631) GitHub issue for more information.
(We don't support older browsers that don't support ES5 methods, but you may find that your apps do work in older browsers if polyfills such as [es5-shim and es5-sham](https://github.com/es-shims/es5-shim) are included in the page. You're on your own if you choose to take this path.)
@ -34,7 +34,7 @@ circle clipPath defs ellipse g image line linearGradient mask path pattern
polygon polyline radialGradient rect stop svg text tspan
```
You may also be interested in [react-art](https://github.com/facebook/react-art), a drawing library for React that can render to Canvas, SVG, or VML (for IE8).
You may also be interested in [react-art](https://github.com/facebook/react-art), a cross-browser drawing library for React.
Ben Alpert
9 years ago