React Time Slice Understanding Analysis

What is time slice?

React time slices are a technique in which React can improve application performance by segmenting tasks into small time slices and then processing tasks in batches. This article will introduce React time slicing and provide a simple tutorial for developers to learn related knowledge.

In a React application, multiple tasks need to be executed simultaneously, such as rendering components, processing user input, updating status, etc. If all tasks are executed at the same time, they will interfere with each other, resulting in a degradation in the performance of the application and a poor user experience. Time slicing is a technique of splitting tasks into small time periods, so that tasks can be run independently and processed in batches.

An important aspect of time slices is task prioritization. React divides tasks into four priorities: Immediate, User-blocking, Normal, and Low. These priorities are key to determining the order in which tasks are completed.

The main advantages of time slices:

• Improve application responsiveness and fluency.
• Running tasks in batches can avoid long-term CPU occupancy.
• Better control over the rendering process so that users can quickly see changes in the application.

How to implement time slicing?

The implementation of React time slices relies on the new Scheduler API. This API serves as a set of tools and algorithms to manage tasks and queue them. Since the React time slicing plugin is already pre-included in create-react-app, you don't need to reconfigure your application.

Here is a simple application that contains some asynchronous tasks that use time slicing:

import React, { useState } from 'react';
import { unstable_scheduleCallback } from 'scheduler';
// Set the priority of tasksconst PRIORITY = {
  IMMEDIATE: 1,
  USER_BLOCKING: 2,
  NORMAL: 3,
  LOW: 4,
};
function App() {
  const [ count, setCount ] = useState(0);
  // Define a time slice task  const sliceTask = ({ priority = , onStart, onEnd }) => {
    unstable_scheduleCallback(priority, () => {
      if (onStart) {
        onStart();
      }
      const result = runAsyncTask();
      if (onEnd) {
        onEnd(result);
      }
    });
  }
  // Simulate an asynchronous task  const runAsyncTask = async () => {
    ('start task');
    await new Promise(resolve => setTimeout(resolve, 1000));
    ('end task');
    return 'done';
  };
  // Process user input  const handleClick = () => {
    setCount(count + 1);
    // Start the time slice task    sliceTask({
      priority: ,
      onStart: () => ('task started'),
      onEnd: result => (`task finished with result ${result}`),
    });
  };
  return (
    <div>
      <p>Count: {count}</p >
      <button onClick={handleClick}>Click Me</button>
    </div>
  );
}
export default App;

In this example, we use the unstable_scheduleCallback method in the Scheduler API to implement time slices, defining a sliceTask function that runs asynchronous tasks. We use the useState hook to save the state, and then call the sliceTask function in the handleClick function to start a time slice task with priority Immediate when the button is clicked.

Summarize

React time slicing is a technique that improves application performance by segmenting tasks into small time slices and then processing tasks in batches. In addition to optimizing application performance, time slicing also provides better control over the rendering process so that users can quickly see changes in the application.

To implement time slicing, React provides the Scheduler API as a set of tools and algorithms to manage tasks and queue them. Developers can use the Scheduler API to implement tasks prioritization and task scheduling to improve application performance and user experience.

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