React 阻止路由离开

import { Prompt } from ‘react-router-dom‘;
<Prompt
    when={true}
    message={location => ‘信息还没保存，确定离开吗？‘}
/>

class Test extends React.Component {
    componentDidMount() {
        this.init();
        window.addEventListener(‘beforeunload‘, this.beforeunload);
    }

    componentWillUnmount = () => {
        window.removeEventListener(‘beforeunload‘, this.beforeunload);
    };

    beforeunload = (ev: any) => {
        if (ev) {
        　　ev.returnValue = ‘‘;
        }
    };

    render() {
        return <div>...</div>
    }
}