javascript - 父子组件是按什么顺序渲染的？

Question

如果我有两个这样的组件(父组件和子组件):

1- parent (倒计时):

var Countdown = React.createClass({
  getInitialState: function(){
    return{count: 0};
  },
  handleSetCountdown: function(seconds){
    this.setState({
      count: seconds
    });
  },
  render:function(){
    var {count} = this.state;
    return(
      <div>
        <Clock totalSeconds={count}/>
        <CountdownForm onSetCountdown={this.handleSetCountdown} />
      </div>
    );
  }
});

module.exports =Countdown;

---

2- child (CountdownForm):

var CountdownForm = React.createClass({
  onSubmit: function(e){
    e.preventDefault();
    var strSeconds = this.refs.seconds.value;
    if(strSeconds.match(/^[0-9]*$/)){
      this.refs.seconds.value ='';
      this.props.onSetCountdown(parseInt(strSeconds,10));

    }
  },
  render: function(){
    return(
      <div>
        <form ref="form" onSubmit={this.onSubmit} className="countdown-form">
          <input type="text" ref="seconds" placeholder="Enter Time In Seconds"/>
          <button className="button expanded">Start</button>
        </form>
      </div>
    );
  }
});

module.exports = CountdownForm;

---

我对生命周期(组件呈现的顺序)感到困惑？

Answer 1

我没有立即在 React 文档中看到明确的“这是父子之间生命周期事件的顺序”，尽管我可能会错过它。

当然，根据经验确定是微不足道的:

class Child extends React.Component {
    constructor(...args) {
        super(...args);
        console.log("Child constructor");
    }
    componentWillMount(...args) {
        console.log("Child componentWillMount");
    }
    componentDidMount(...args) {
        console.log("Child componentDidMount");
    }
    render() {
        console.log("Child render");
        return <div>Hi there</div>;
    }
}

class Parent extends React.Component {
    constructor(...args) {
        super(...args);
        console.log("Parent constructor");
    }
    componentWillMount(...args) {
        console.log("Parent componentWillMount");
    }
    componentDidMount(...args) {
        console.log("Parent componentDidMount");
    }
    render() {
        console.log("Parent render start");
        const c = <Child />;
        console.log("Parent render end");
        return c;
    }
}

ReactDOM.render(<Parent />, document.getElementById("react"));

.as-console-wrapper {
  max-height: 100% !important;
}

<div id="react"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

这向我们展示了顺序:

Parent constructor
Parent componentWillMount
Parent render start
Parent render end
Child constructor
Child componentWillMount
Child render
Child componentDidMount
Parent componentDidMount

Which got me wondering about the order of children within a parent, so:

class Child extends React.Component {
    constructor(props, ...rest) {
        super(props, ...rest);
        console.log(this.props.name + " constructor");
    }
    componentWillMount(...args) {
        console.log(this.props.name + " componentWillMount");
    }
    componentDidMount(...args) {
        console.log(this.props.name + " componentDidMount");
    }
    render() {
        console.log(this.props.name + " render");
        return <div>Hi from {this.props.name}!</div>;
    }
}

class Parent extends React.Component {
    constructor(...args) {
        super(...args);
        console.log("Parent constructor");
    }
    componentWillMount(...args) {
        console.log("Parent componentWillMount");
    }
    componentDidMount(...args) {
        console.log("Parent componentDidMount");
    }
    render() {
        console.log("Parent render start");
        const result =
            <div>
                <Child name="Child1" />
                <Child name="Child2" />
            </div>;
        console.log("Parent render end");
        return result;
    }
}

ReactDOM.render(<Parent />, document.getElementById("react"));

.as-console-wrapper {
  max-height: 100% !important;
}

<div id="react"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

这给了我们:

Parent constructor
Parent componentWillMount
Parent render start
Parent render end
Child1 constructor
Child1 componentWillMount
Child1 render
Child2 constructor
Child2 componentWillMount
Child2 render
Child1 componentDidMount
Child2 componentDidMount
Parent componentDidMount

一点也不奇怪，但值得仔细检查。 :-)