Sebastian MarkbågeandGitHub
28b8d7dcaf
Stacked on #30960 and #30966. Behind the enableComponentPerformanceTrack flag. This is the first step of performance logging. This logs the start and end time of a component render in the passive effect phase. We use the data we're already tracking on components when the Profiler component or DevTools is active in the Profiling or Dev builds. By backdating this after committing we avoid adding more overhead in the hot path. By only logging things that actually committed, we avoid the costly unwinding of an interrupted render which was hard to maintain in earlier versions. We already have the start time but we don't have the end time. That's because `actualStartTime + actualDuration` isn't enough since `actualDuration` counts the actual CPU time excluding yields and suspending in the render. Instead, we infer the end time to be the start time of the next sibling or the complete time of the whole root if there are no more siblings. We need to pass this down the passive effect tree. This will mean that any overhead and yields are attributed to this component's span. In a follow up, we'll need to start logging these yields to make it clear that this is not part of the component's self-time. In follow ups, I'll do the same for commit phases. We'll also need to log more information about the phases in the top track. We'll also need to filter out more components from the trees that we don't need to highlight like the internal Offscreen components. It also needs polish on colors etc. Currently, I place the components into separate tracks depending on which lane currently committed. That way you can see what was blocking Transitions or Suspense etc. One problem that I've hit with the new performance.measure extensions is that these tracks show up in the order they're used which is not the order of priority that we use. Even when you add fake markers they have to actually be within the performance run since otherwise the calls are noops so it's not enough to do that once. However, I think this visualization is actually not good because these trees end up so large that you can't see any other lanes once you expand one. Therefore, I think in a follow up I'll actually instead switch to a model where Components is a single track regardless of lane since we don't currently have overlap anyway. Then the description about what is actually rendering can be separate lanes. <img width="1512" alt="Screenshot 2024-09-15 at 10 55 55 PM" src="https://github.com/user-attachments/assets/5ca3fa74-97ce-40c7-97f7-80c1dd7d6470"> <img width="1512" alt="Screenshot 2024-09-15 at 10 56 27 PM" src="https://github.com/user-attachments/assets/557ad65b-4190-465f-843c-0bc6cbb9326d">
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.