关于前端:React-import按需异步加载asyncComponent

import()办法返回的是一个Promise。
asyncComponent是一个返回组件的函数

const asyncComponent = (importComponent) => {    return class extends Component {        constructor(){            super();            this.state = {                component: null            }        }        componentDidMount() {            importComponent().then(cmp => {                this.setState({                    component: cmp.default                });            });        }        render() {            const C = this.state.component;            return C ? <C {...this.props} /> : null        }    }}

应用：

const Home = AsyncCompoent(() => import('./Home/index/js'));const City = AsyncCompoent(() => {    impirt('./city/index.js')});