Implementation example of synthetic events in React

User interaction is an integral part of building modern web applications. React, as a popular JavaScript library, provides efficient and flexible ways to handle these user interactions. React's event processing model is significantly different from the traditional DOM event system, and one of the important concepts is "synthesis events". This article will explore in-depth synthetic events in React, including their definitions, working principles, comparisons with native events, how to use synthetic events, and best practices.

1. Definition of synthetic events

Synthetic Events are React encapsulation of browser native events. It is a cross-browser event interface, allowing developers to handle events in a consistent way without worrying about differences between different browsers. Synthetic events are widely used in React, which can simplify event processing and improve performance.

Synthetic events provide an API similar to native events, but the way it is used and the implementation mechanism behind it is slightly different from the traditional event handling method. Synthesis events occur to improve the convenience of development and reduce errors caused by browser differences.

2. How the working principle of synthetic events

1. Structure of event system

In React, the working principle of synthetic events is achieved through event delegating. React registers event listeners on top-level components, rather than on every DOM element. This method not only reduces memory usage, but also improves performance.

When an event is triggered, React will pass event information to the corresponding event handler function by synthesizing event objects. These synthetic event objects have all properties of native events and are a lightweight wrapper.

2. The life cycle of events

The life cycle of synthetic events is similar to that of native events, but there are some significant differences. Synthetic event objects are recycled after event handling function calls, so they cannot be accessed asynchronously.

• Event trigger: When the user interacts with the component (such as clicks, inputs, focus, etc.), the synthesis event will be triggered.
• Event object creation:React creates a synthetic event object and passes it to the event handler function.
• Event handling: Developers use the properties of synthetic event objects in event handling functions.
• Event object recycling: The synthetic event object will be recycled after the event processing function call to ensure that there is no memory leak.

3. Comparison between synthetic events and native events

3. How to use synthetic events

Using synthesis events is very simple, developers can directly bind event handling functions to elements of components using event handling properties in JSX.

1. Basic examples

Here is a simple example showing how to use synthetic events in React:

import React from 'react';

class ClickButton extends  {
  handleClick = (event) => {
    ('Button clicked!', event);
  };

  render() {
    return (
      <button onClick={}>
        Click Me
      </button>
    );
  }
}

export default ClickButton;

In this example, we define ahandleClickMethod and bind it to the button'sonClickevent. When the user clicks the button, the synthetic event object will be passed as a parameter tohandleClickMethod and output relevant information on the console.

2. Access the synthetic event object

Synthetic event objects are similar to native event objects and provide multiple useful properties, such astype、targetandcurrentTargetwait. We can access these properties through the parameters of the event handler function.

handleClick = (event) => {
  ('Event Type:', ); // Output event type  ('Target Element:', ); // Output event target};

3. Prevent default behavior and event propagation

Synthesized event objects also contain methods that block default behavior, such as()and(). This is especially important when handling form submissions or link clicks.

handleSubmit = (event) => {
  (); // Block form submission by default  ('Form submitted');
};

4. Best practices for synthetic events

1. Use synthetic events instead of native events

Always use React's synthetic events instead of manipulating native events directly. This ensures code consistency and cross-browser compatibility.

2. Avoid asynchronous access to synthetic event objects

Since synthetic event objects are recycled after the event handling function call, make sure to use these objects inside the event handling function. Avoid accessing synthetic event objects in asynchronous operations, as it may have been recycled.

3. Clean up the event listener

If you use event listeners in your component, make sure to clean them when the component is uninstalled to avoid memory leaks. For example, in usecomponentDidMountWhen adding event listeners, remember tocomponentWillUnmountRemove them in  .

class MyComponent extends  {
  componentDidMount() {
    ('resize', );
  }

  componentWillUnmount() {
    ('resize', );
  }

  handleResize = () => {
    ('Window resized');
  };

  render() {
    return <div>Resize the window!</div>;
  }
}

4. Performance of event handling functions

When you need to pass parameters to event handling functions, you can use arrow functions orbindmethod. Note that using arrow functions creates a new function instance every time you render, which may affect performance. In performance-sensitive occasions, consider passing parameters tobindIn the method.

handleClick = (param) => {
  (param);
};

render() {
  return (
    <button onClick={(this, 'Hello')}>
      Click Me
    </button>
  );
}

5. Frequently Asked Questions about Synthesis Events

1. How compatible are the synthetic events?

Synthesis events provide a consistent interface to ensure consistent behavior across browsers. Whether it’s Chrome, Firefox, or Safari, synthesis events work properly, simplifying the complexity of cross-browser development.

2. Does the synthetic event object support all properties of the native event?

Synthetic event objects provide APIs similar to native events, covering most commonly used properties and methods. For example,、、()wait. However, some specific native event properties may not apply.

3. How to deal with event bubbles and capture?

React uses event bubbles to handle events. In React, event handlers can be triggered during the bubbling phase. Can be used in event handlers()Method to prevent the event from spreading.

6. Summary

Synthetic events are a core part of the React event handling mechanism, which simplifies event handling and cross-browser compatibility issues by encapsulating native events. Synthesis events provide a consistent interface that allows developers to handle user interactions easily.

By using synthesis events, developers can improve the maintainability and performance of their code and ensure consistency of user experience. In actual development, following best practices can help you manage events effectively and improve your application's responsiveness and stability.

This is the end of this article about the implementation example of synthetic events in React. For more related React synthesis events, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!