Sebastian Markbåge
d4688dfaaf
This tracks the current window.event.timeStamp the first time we setState or call startTransition. For either the blocking track or transition track. We can use this to show how long we were blocked by other events or overhead from when the user interacted until we got called into React. Then we track the time we start awaiting a Promise returned from startTransition. We can use this track how long we waited on an Action to complete before setState was called. Then finally we track when setState was called so we can track how long we were blocked by other word before we could actually start rendering. For a Transition this might be blocked by Blocking React render work. We only log these once a subsequent render actually happened. If no render was actually scheduled, then we don't log these. E.g. if an isomorphic Action doesn't call startTransition there's no render so we don't log it. We only log the first event/update/transition even if multiple are batched into it later. If multiple Actions are entangled they're all treated as one until an update happens. If no update happens and all entangled actions finish, we clear the transition so that the next time a new sequence starts we can log it. We also clamp these (start the track later) if they were scheduled within a render/commit. Since we share a single track we don't want to create overlapping tracks. The purpose of this is not to show every event/action that happens but to show a prelude to how long we were blocked before a render started. So you can follow the first event to commit. <img width="674" alt="Screenshot 2024-09-20 at 1 59 58 AM" src="https://github.com/user-attachments/assets/151ba9e8-6b3c-4fa1-9f8d-e3602745eeb7"> I still need to add the rendering/suspended phases to the timeline which why this screenshot has a gap. <img width="993" alt="Screenshot 2024-09-20 at 12 50 27 AM" src="https://github.com/user-attachments/assets/155b6675-b78a-4a22-a32b-212c15051074"> In this case it's a Form Action which started a render into the form which then suspended on the action. The action then caused a refresh, which interrupts with its own update that's blocked before rendering. Suspended roots like this is interesting because we could in theory start working on a different root in the meantime which makes this timeline less linear.
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 the 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 project.
Installation
React has been designed for gradual adoption from the start, and you can use as little or as much React as you need:
- Use Quick Start to get a taste of React.
- Add React to an Existing Project to use as little or as much React as you need.
- Create a New React App if you're looking for a powerful JavaScript toolchain.
Documentation
You can find the React documentation on the website.
Check out the Getting Started page for a quick overview.
The documentation is divided into several sections:
- Quick Start
- Tutorial
- Thinking in React
- Installation
- Describing the UI
- Adding Interactivity
- Managing State
- Advanced Guides
- API Reference
- Where to Get Support
- Contributing Guide
You can improve it by sending pull requests to this repository.
Examples
We have several examples on the website. Here is the first one to get you started:
import { createRoot } from 'react-dom/client';
function HelloMessage({ name }) {
return <div>Hello {name}</div>;
}
const root = createRoot(document.getElementById('container'));
root.render(<HelloMessage name="Taylor" />);
This example will render "Hello Taylor" 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.
Contributing
The main purpose of this repository is to continue evolving 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.
Good First Issues
To help you get your feet wet and get you familiar with our contribution process, we have a list of good first issues that contain bugs that have a relatively limited scope. This is a great place to get started.
License
React is MIT licensed.