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React components render order All In One

components render order / components lifecycle

DOM tree render order

React diff

React fiber

当父组件进行重新渲染操作时，即使子组件的props或state没有做出任何改变，也会同样进行重新渲染

当子组件进行重新渲染操作时，只有子组件会同样进行重新渲染

parent component change props

import Parent from "./components/parent";

export default function App() {
  const [name, setName] = useState(`xgqfrms`);
  const [show, setShow] = useState(true);
  const toggleShow = () => {
    setShow(!show);
  };
  const updateName = () => {
    setName(`webfullstack`);
  };
  useEffect(() => {
    // Update the document title using the browser API
    let flag = true;
    if (flag) {
      document.title = `react hooks ${show}`;
    }
    // cancel promise
    return () => (flag = false);
  }, [show]);
  return (
    <div className="App">
      <h1>react-parent-child-lifecycle-order</h1>
      <button onClick={toggleShow}>toggleShow</button>
      <p>update props name</p>
      <button onClick={updateName}>updateName</button>
      {show && <Parent name={name}/>}
    </div>
  );
}

parent component change state

import React, { Component } from "react";

import Child from "./child";
import log from "../utils/log";

class Parent extends Component {
  constructor(props) {
    super();
    this.state = {
      show: true,
      randomName: props.name,// "xgqfrms"
    };
    this.toggleShow = this.toggleShow.bind(this);
    log(`parent constructor`, 0);
  }
  getRandomName = () => {
    const randomName = Math.random() > 0.5 ? `abc` : `xyz`;
    this.setState({
      randomName,
    });
  };
  toggleShow = () => {
    const { show } = this.state;
    this.setState({
      show: !show
    });
  };
  componentWillMount() {
    log(`parent WillMount`, 1);
  }
  // UNSAFE_componentWillMount() {
  //   log(`parent UNSAFE_WillMount`, 1);
  // }
  componentDidMount() {
    log(`parent DidMount`, 2);
  }
  componentWillReceiveProps() {
    log(`parent WillReceiveProps`, 3);
  }
  // UNSAFE_componentWillReceiveProps() {
  //   log(`parent UNSAFE_WillReceiveProps`, 3);
  // }
  shouldComponentUpdate() {
    log(`parent shouldComponentUpdate`, 4);
    return true;
    // return true or false;
  }
  componentWillUpdate() {
    log(`parent WillUpdate`, 5);
  }
  // UNSAFE_componentWillUpdate() {
  //   log(`parent UNSAFE_WillUpdate`, 5);
  // }
  componentDidUpdate() {
    log(`parent DidUpdate`, 6);
  }
  componentWillUnmount() {
    log(`

parent WillUnmount`, 7);
  }
  componentDidCatch(err) {
    log(`parent DidCatch`, err);
  }
  render() {
    log(`parent render`);
    const {
      show,
      randomName,
    } = this.state;
    return (
      <div className="parent">
        <h1>parent-lifecycle-order</h1>
        <button onClick={this.getRandomName}>get random name</button>
        <p>randomName = {randomName}</p>
        <button onClick={this.toggleShow}>toggleShow</button>
        {show && <Child />}
      </div>
    );
  }
}

export default Parent;

child component change state

demos

https://codesandbox.io/s/react-parent-child-lifecycle-order-update-parent-state-render-render-2559w

refs

https://stackoverflow.com/questions/44654982/in-which-order-are-parent-child-components-rendered

https://scotch.io/courses/getting-started-with-react/parent-child-component-communication

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