如何在 react.js 中收听 localstorage-前端问题

How to listen to localstorage in react.js(如何在 react.js 中收听 localstorage)

本文介绍了如何在 react.js 中收听 localstorage的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我在使用从本地存储中的数组获取数据的组件时遇到问题.它在页面加载时获取初始数据，但是当 localstorage 更改时如何更新?

I'm having a problem with a component that gets data from an array in localstorage. It gets the initial data when the page loads, but how do I update when localstorage is changed?

import React, {Component} from 'react'; 
    class MovieList extends Component {
       constructor(props){
          super(props)
            this.state = {
            filmList: []     
          }
       }    
      componentWillMount(){
          var film = [],
          keys = Object.keys(localStorage),
          i = keys.length;
          while ( i-- ) {
             film.push( localStorage.getItem(keys[i]))     
          }
          this.setState({filmList: film})

      };

      render(){
        return(
           <ul>
              <li>{this.state.filmlist}</li>            
           </ul>

        );
    }

}

export default MovieList;

推荐答案

根据 Mozilla 的 Web API 文档，有一个 StorageEvent 会在对 Storage 进行更改时触发对象.

Per Mozilla's Web API docs there's a StorageEvent that gets fired whenever a change is made to the Storage object.

我在我的应用程序中创建了一个警报组件，只要对特定的 localStorage 项进行更改，该组件就会关闭.我会添加一个代码片段供您运行，但由于跨域问题，您无法通过它访问 localStorage.

I created an Alert component within my application that would go off whenever a change was made to a specific localStorage item. I would've added a code snippet for you to run but you can't access localStorage through it due to cross-origin issues.

class Alert extends React.Component {
    constructor(props) {
        super(props)
        this.agree = this.agree.bind(this)
        this.disagree = this.disagree.bind(this)
        this.localStorageUpdated = this.localStorageUpdated.bind(this)
        this.state = {
            status: null
        }
    }
    componentDidMount() {
        if (typeof window !== 'undefined') {
            this.setState({status: localStorage.getItem('localstorage-status') ? true : false})

            window.addEventListener('storage', this.localStorageUpdated)
        }
    }
    componentWillUnmount(){
        if (typeof window !== 'undefined') {
            window.removeEventListener('storage', this.localStorageUpdated)
        }
    }
    agree(){
        localStorage.setItem('localstorage-status', true)
        this.updateState(true)
    }
    disagree(){
        localStorage.setItem('localstorage-status', false)
        this.updateState(false)
    }
    localStorageUpdated(){
        if (!localStorage.getItem('localstorage-status')) {
            this.updateState(false)
        } 
        else if (!this.state.status) {
            this.updateState(true)
        }
    }
    updateState(value){
        this.setState({status:value})
    }
    render () {
        return( !this.state.status ? 
            <div class="alert-wrapper">
                <h3>The Good Stuff</h3>
                <p>Blah blah blah</p>
                <div class="alert-button-wrap">
                    <button onClick={this.disagree}>Disagree</button>
                    <button onClick={this.agree}>Agree</button>
                </div>
            </div>
         : null )
    }
}