React 父组件 子组件之间的传值

1、父组件向子组件传值：

父组件 App.js：

import React,{ Component } from "react";
import Sub from "./SubComponent.js";
import "./App.css";

export default class App extends Component{

    render(){
        return(
            <div>
                <Sub title = "今年过节不收礼" />
            </div>
        )
    }
}

子组件 SubComponent.js：

import React from "react";

const Sub = (props) => {
    return(
        <h1>
            { props.title }
        </h1>
    )
}

export default Sub;

2、子组件向父组件传值：

子组件 SubComponent.js：

import React from "react";

const Sub = (props) => {
    const cb = (msg) => {
        return () => {
            props.callback(msg)
        }
    }
    return(
        <div>
            <button onClick = { cb("我们通信把") }>点击我</button>
        </div>
    )
}

export default Sub;

父组件 App.js：

import React,{ Component } from "react";
import Sub from "./SubComponent.js";
import "./App.css";

export default class App extends Component{
    callback(msg){
        console.log(msg);
    }
    render(){
        return(
            <div>
                <Sub callback = { this.callback.bind(this) } />
            </div>
        )
    }
}