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深入了解React中的合成事件

作者：跑跑快跑

React 中的事件，是对原生事件的封装，叫做合成事件。这篇文章主要通过几个简单的示例为大家详细介绍一下React中的合成事件，感兴趣的可以了解一下

1 事件三个阶段 捕获、目标、处理 （具体百度，后面有空补全）

2 示例

import React from "react";
 
class Test extends React.Component {
  parentRef;
  childRef;
  constructor(props) {
    super(props);
    this.parentRef = React.createRef();
    this.childRef = React.createRef();
  }
  componentDidMount() {
    document.addEventListener(
      "click",
      () => {
        console.log(`document原生事件捕获`);
      },
      true
    );
    document.addEventListener("click", () => {
      console.log(`document原生事件冒泡`);
    });
    this.parentRef.current.addEventListener(
      "click",
      () => {
        console.log(`父元素原生事件捕获`);
      },
      true
    );
    this.parentRef.current.addEventListener("click", () => {
      console.log(`父元素原生事件冒泡`);
    });
    this.childRef.current.addEventListener(
      "click",
      () => {
        console.log(`子元素原生事件捕获`);
      },
      true
    );
    this.childRef.current.addEventListener("click", () => {
      console.log(`子元素原生事件冒泡`);
    });
  }
  handleParentBubble = () => {
    console.log(`父元素React事件冒泡`);
  };
  handleChildBubble = (e) => {
    console.log(`子元素React事件冒泡`);
  };
  handleParentCapture = () => {
    console.log(`父元素React事件捕获`);
  };
  handleChileCapture = () => {
    console.log(`子元素React事件捕获`);
  };
  render() {
    return (
      <div
        ref={this.parentRef}
        onClick={this.handleParentBubble}
        onClickCapture={this.handleParentCapture}
      >
        <div
          ref={this.childRef}
          onClick={this.handleChildBubble}
          onClickCapture={this.handleChileCapture}
        >
          事件处理测试
        </div>
      </div>
    );
  }
}
 
export default Test;

执行顺序

只留子元素修改代码

import React from "react";
 
class Test extends React.Component {
  parentRef;
  childRef;
  constructor(props) {
    super(props);
    this.parentRef = React.createRef();
    this.childRef = React.createRef();
  }
  componentDidMount() {
    document.addEventListener(
      "click",
      () => {
        console.log(`document原生事件捕获`);
      },
      true
    );
    document.addEventListener("click", () => {
      console.log(`document原生事件冒泡`);
    });
    // this.parentRef.current.addEventListener(
    //   "click",
    //   () => {
    //     console.log(`父元素原生事件捕获`);
    //   },
    //   true
    // );
    // this.parentRef.current.addEventListener("click", () => {
    //   console.log(`父元素原生事件冒泡`);
    // });
    this.childRef.current.addEventListener(
      "click",
      () => {
        console.log(`子元素原生事件捕获`);
      },
      true
    );
    this.childRef.current.addEventListener("click", () => {
      console.log(`子元素原生事件冒泡`);
    });
  }
  // handleParentBubble = () => {
  //   console.log(`父元素React事件冒泡`);
  // };
  handleChildBubble = (e) => {
    console.log(`子元素React事件冒泡`);
  };
  // handleParentCapture = () => {
  //   console.log(`父元素React事件捕获`);
  // };
  handleChileCapture = () => {
    console.log(`子元素React事件捕获`);
  };
  render() {
    return (
      <div
        ref={this.childRef}
        onClick={this.handleChildBubble}
        onClickCapture={this.handleChileCapture}
      >
        事件处理测试
      </div>
    );
    return (
      <div
        ref={this.parentRef}
        onClick={this.handleParentBubble}
        onClickCapture={this.handleParentCapture}
      >
        <div
          ref={this.childRef}
          onClick={this.handleChildBubble}
          onClickCapture={this.handleChileCapture}
        >
          事件处理测试
        </div>
      </div>
    );
  }
}
 
export default Test;

document原生事件捕获--》子元素React事件捕获--》子元素原生事件捕获--》子元素原生事件冒泡--》子元素React事件冒泡--》document原生事件冒泡

从这个执行顺序来看，react事件捕获执行比原生事件捕获早，但是原生事件冒泡执行比react事件冒泡快。

所有的react捕获事件执行完毕之后才会去执行原生的捕获事件（document原生事件捕获最先执行）

3 子元素阻止react事件冒泡

e.stopPropagation();

import React from "react";
 
class Test extends React.Component {
  parentRef;
  childRef;
  constructor(props) {
    super(props);
    this.parentRef = React.createRef();
    this.childRef = React.createRef();
  }
  componentDidMount() {
    document.addEventListener(
      "click",
      () => {
        console.log(`document原生事件捕获`);
      },
      true
    );
    document.addEventListener("click", () => {
      console.log(`document原生事件冒泡`);
    });
    this.parentRef.current.addEventListener(
      "click",
      () => {
        console.log(`父元素原生事件捕获`);
      },
      true
    );
    this.parentRef.current.addEventListener("click", () => {
      console.log(`父元素原生事件冒泡`);
    });
    this.childRef.current.addEventListener(
      "click",
      () => {
        console.log(`子元素原生事件捕获`);
      },
      true
    );
    this.childRef.current.addEventListener("click", () => {
      console.log(`子元素原生事件冒泡`);
    });
  }
  handleParentBubble = () => {
    console.log(`父元素React事件冒泡`);
  };
  handleChildBubble = (e) => {
    e.stopPropagation();
    console.log(`子元素React事件冒泡`);
  };
  handleParentCapture = () => {
    console.log(`父元素React事件捕获`);
  };
  handleChileCapture = () => {
    console.log(`子元素React事件捕获`);
  };
  render() {
    return (
      <div
        ref={this.parentRef}
        onClick={this.handleParentBubble}
        onClickCapture={this.handleParentCapture}
      >
        <div
          ref={this.childRef}
          onClick={this.handleChildBubble}
          onClickCapture={this.handleChileCapture}
        >
          事件处理测试
        </div>
      </div>
    );
  }
}
 
export default Test;

执行顺序

e.stopPropagation()只能阻止react合成事件的冒泡和document原生事件冒泡，并不能阻止自己和父元素原生事件的冒泡。

e.nativeEvent.stopImmediatePropagation()只能阻止document原生事件冒泡。

e.preventDefault()和不执行一样

e.nativeEvent.stopPropagation()只能阻止document原生事件冒泡。

如果我们在子原生的原声事件里面阻止冒泡，都阻止了。

import React from "react";
 
class Test extends React.Component {
  parentRef;
  childRef;
  constructor(props) {
    super(props);
    this.parentRef = React.createRef();
    this.childRef = React.createRef();
  }
  componentDidMount() {
    document.addEventListener(
      "click",
      () => {
        console.log(`document原生事件捕获`);
      },
      true
    );
    document.addEventListener("click", () => {
      console.log(`document原生事件冒泡`);
    });
    this.parentRef.current.addEventListener(
      "click",
      () => {
        console.log(`父元素原生事件捕获`);
      },
      true
    );
    this.parentRef.current.addEventListener("click", () => {
      console.log(`父元素原生事件冒泡`);
    });
    this.childRef.current.addEventListener(
      "click",
      () => {
        console.log(`子元素原生事件捕获`);
      },
      true
    );
    this.childRef.current.addEventListener("click", (e) => {
      e.stopPropagation();
      console.log(`子元素原生事件冒泡`);
    });
  }
  handleParentBubble = () => {
    console.log(`父元素React事件冒泡`);
  };
  handleChildBubble = (e) => {
    console.log(`子元素React事件冒泡`);
  };
  handleParentCapture = () => {
    console.log(`父元素React事件捕获`);
  };
  handleChileCapture = () => {
    console.log(`子元素React事件捕获`);
  };
  render() {
    return (
      <div
        ref={this.parentRef}
        onClick={this.handleParentBubble}
        onClickCapture={this.handleParentCapture}
      >
        <div
          ref={this.childRef}
          onClick={this.handleChildBubble}
          onClickCapture={this.handleChileCapture}
        >
          事件处理测试
        </div>
      </div>
    );
  }
}
 
export default Test;

执行顺序

在子元素的原声事件里面，阻止了所有的冒泡。同时也阻止了react事件。

在父元素原生事件中阻止冒泡

import React from "react";
 
class Test extends React.Component {
  parentRef;
  childRef;
  constructor(props) {
    super(props);
    this.parentRef = React.createRef();
    this.childRef = React.createRef();
  }
  componentDidMount() {
    document.addEventListener(
      "click",
      () => {
        console.log(`document原生事件捕获`);
      },
      true
    );
    document.addEventListener("click", () => {
      console.log(`document原生事件冒泡`);
    });
    this.parentRef.current.addEventListener(
      "click",
      () => {
        console.log(`父元素原生事件捕获`);
      },
      true
    );
    this.parentRef.current.addEventListener("click", (e) => {
      e.stopPropagation();
      console.log(`父元素原生事件冒泡`);
    });
    this.childRef.current.addEventListener(
      "click",
      () => {
        console.log(`子元素原生事件捕获`);
      },
      true
    );
    this.childRef.current.addEventListener("click", (e) => {
      console.log(`子元素原生事件冒泡`);
    });
  }
  handleParentBubble = () => {
    console.log(`父元素React事件冒泡`);
  };
  handleChildBubble = (e) => {
    console.log(`子元素React事件冒泡`);
  };
  handleParentCapture = () => {
    console.log(`父元素React事件捕获`);
  };
  handleChileCapture = () => {
    console.log(`子元素React事件捕获`);
  };
  render() {
    return (
      <div
        ref={this.parentRef}
        onClick={this.handleParentBubble}
        onClickCapture={this.handleParentCapture}
      >
        <div
          ref={this.childRef}
          onClick={this.handleChildBubble}
          onClickCapture={this.handleChileCapture}
        >
          事件处理测试
        </div>
      </div>
    );
  }
}
 
export default Test;

执行顺序

父元素原生事件中阻止冒泡阻止了react事件

阻止document原生事件的冒泡并不会阻止了react事件

 document.addEventListener("click", (e) => {
      e.stopPropagation();
      console.log(`document原生事件冒泡`);
 });

结论

react捕获事件快于原生捕获事件的执行

react冒泡事件慢于原生冒泡事件的执行

原生冒泡事件会阻止react事件。

以上就是深入了解React中的合成事件的详细内容，更多关于React合成事件的资料请关注脚本之家其它相关文章！

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