Sebastian MarkbågeandGitHub
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* Warn for text content * Warn for different attributes/properties values Warns if there are unknown extra attributes in the hydrated node. It also tries to compare the existing property or attribute against the expected value. It does this by reading the property and comparing it to the prop. Except it's not that simple because multiple prop values can yield the same output. For this we pass an extra expected value that is a hint as to which one was used. This is a bit weird but I'm not sure the alternatives were much better. * Warn when there is an insertion or deletion during hydration This warns if there is ever an insertion or deletion due to hydration failing to find a match. Currently we can't warn for insertions required into the root because that's how we do all non-hydrating renders atm. Left a todo. This strategy is a bit unfortunate that it leads to so much plumbing code. And we have to add three extra methods to the HostConfig that are only used in DEV and not for anything else. I don't really have a better idea. * Don't try to delete children of a textarea Textareas are special cases. The initial mount inserts children as the default value, but we should leave that untouched. This is the same as the special case where we set text content of children so I'll use that mechanism. * Change expected format for text differences In Stack this is presented as HTML which needs to have normalized escaping rules. In Fiber it is currently not presented as HTML but a raw string so we don't escape it. * Unmount component in between tests In Fiber, the second warning isn't issued because it's considered an update not a new initial render and we don't fire the warning for those. * Change expectation of white space text behavior in Fiber In Fiber we don't expect empty strings to be different from rendering null. In fact, in a follow up I plan on formalizing this by never creating text Fibers for empty strings. * Warn for different dangerouslySetInnerHTML We can't just compare the raw innerHTML value because it will have been normalized. Instead, we'll create another element, set its innerHTML and read it back. Since there can be custom elements registered with this document, we want to avoid any side-effects they might cause. So I do this in a fresh new document. I'm not sure how this would affect controlled components and other stuff that could have changed after runtime. I think for those cases maybe we just need a general way of opting out of the diff.
React · 
React is a JavaScript library for building user interfaces.
- Declarative: React makes it painless to create interactive UIs. Design simple views for each state in your application, and React will efficiently update and render just the right components when your data changes. Declarative views make your code more predictable, simpler to understand, and easier to debug.
- Component-Based: Build encapsulated components that manage their own state, then compose them to make complex UIs. Since component logic is written in JavaScript instead of templates, you can easily pass rich data through your app and keep state out of the DOM.
- Learn Once, Write Anywhere: We don't make assumptions about the rest of your technology stack, so you can develop new features in React without rewriting existing code. React can also render on the server using Node and power mobile apps using React Native.
Learn how to use React in your own project.
Examples
We have several examples on the website. Here is the first one to get you started:
class HelloMessage extends React.Component {
render() {
return <div>Hello {this.props.name}</div>;
}
}
ReactDOM.render(
<HelloMessage name="John" />,
document.getElementById('container')
);
This example will render "Hello John" into a container on the page.
You'll notice that we used an HTML-like syntax; we call it JSX. JSX is not required to use React, but it makes code more readable, and writing it feels like writing HTML. We recommend using Babel with a React preset to convert JSX into native JavaScript for browsers to digest.
Installation
React is available as the react package on npm. It is also available on a CDN.
React is flexible and can be used in a variety of projects. You can create new apps with it, but you can also gradually introduce it into an existing codebase without doing a rewrite.
The recommended way to install React depends on your project. Here you can find short guides for the most common scenarios:
Contributing
The main purpose of this repository is to continue to evolve React core, making it faster and easier to use. Development of React happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving React.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React.
Beginner Friendly Bugs
To help you get your feet wet and get you familiar with our contribution process, we have a list of beginner friendly bugs that contain bugs which are fairly easy to fix. This is a great place to get started.
License
React is BSD licensed. We also provide an additional patent grant.
React documentation is Creative Commons licensed.
Examples provided in this repository and in the documentation are separately licensed.