bvaughn

// This is an advanced example! It is not typically required for application code.
// If you are using a library like Redux or MobX, use the container component provided by that library.
// If you are authoring such a library, use the technique shown below.

// This example shows how to safely update subscriptions in response to props changes.
// In this case, it is important to wait until `componentDidUpdate` before removing a subscription.
// In the event that a render is cancelled before being committed, this will prevent us from unsubscribing prematurely.

// We also need to be careful about how we handle events that are dispatched in between
// `getDerivedStateFromProps` and `componentDidUpdate` so that we don't put stale values into the `state`.

bvaughn

// This is an example of how to fetch external data in response to updated props,
// If you are using an async mechanism that does not support cancellation (e.g. a Promise).

class ExampleComponent extends React.Component {
  _currentId = null;

  state = {
    externalData: null
  };

bvaughn

// This is an advanced example! It is not intended for use in application code.
// Libraries like Relay may make use of this technique to save some time on low-end mobile devices.
// Most components should just initiate async requests in componentDidMount.

class ExampleComponent extends React.Component {
  _hasUnmounted = false;

  state = {
    externalData: null,
  };

sebmarkbage

let cache = new Map();
let pending = new Map();

function fetchTextSync(url) {
  if (cache.has(url)) {
    return cache.get(url);
  }
  if (pending.has(url)) {
    throw pending.get(url);
  }

drufball

Infinite list: Automatically lazy-loads content from a data source as the user scrolls, view-recycling as necessary.

Lazy-load image: Won't load the resource until it is on or near the screen.

Pull to refresh: Recreate the "pull down to refresh" UI from iOS and Android.

Carousel: Side scroller that handles lazy-loading and optionally snaps to elements.

Multi-line ellipsis: Automatically hide text and replace with a fade/ellipsis after a specified number of lines.

acdlite

Demo: Coordinating async React with non-React views

tl;dr I built a demo illustrating what it might look like to add async rendering to Facebook's commenting interface, while ensuring it appears on the screen simultaneous to the server-rendered story.

A key benefit of async rendering is that large updates don't block the main thread; instead, the work is spread out and performed during idle periods using cooperative scheduling.

But once you make something async, you introduce the possibility that things may appear on the screen at separate times. Especially when you're dealing with multiple UI frameworks, as is often the case at Facebook.

How do we solve this with React?

addyosmani

Some quick thoughts on https://twitter.com/dan_abramov/status/884892244817346560. It's not ignorant at all to ask how browser vendors approach performance. On the V8 side we've discussed bytecode precompilation challenges a few times this year. Here's my recollection of where we stand on the idea:

JavaScript engines like V8 have to work on multiple architectures. Every version of V8 is different. The architectures we target are different. A precompiled bytecode solution would require a system (e.g the server or a CDN) to generate bytecode builds for every target architecture, every version of V8 supported and every version of the JavaScript libraries or bundles bytecode is being generated for. This is because we would need to make sure every user accessing a page using that bytecode can still get the final JS successfully executed.

Consider that if a cross-browser solution to this problem was desired, the above would need to be applied to JavaScriptCore, SpiderMonkey and Chakra as well. It would need to ca

sebmarkbage

type FrameScope = {
  [key:string]: mixed
};
type StackFrame = {
  name?: string,
  fileName?: string,
  lineNumber?: number,
  columnNumber?: number,
  scope?: FrameScope
};

jinuljt

清除safari缓存即可。  
原理是因为Apple限制，在iOS上微信只能使用webview。

chourobin

Bridging Native & React for iOS & Android

js -> native

• Simple Example
• Callbacks
• Promises
• Properties

native -> js