1、工具類storage.js

var app ={
    set(key,value){
        localStorage.setItem(key,JSON.stringify(value));
    },
    get(key){
        return JSON.parse(localStorage.getItem(key));
    },
    delete(key){
        localStorage.removeItem(key);
    },
    countFalseNum(key){
        let count=new Number(0
 
);
        let list = JSON.parse(localStorage.getItem(key));
        list.map(function (value,key) {
            if(value.checked==false){
                count = count+1;
            }
        })
        return count;
    },
    countTrueNum(key){
        let count=new Number(0);
        let list = JSON.parse(localStorage.getItem(key));
        list.map(function (value,key) {
            
 
if(value.checked==false){
                count = count+1;
            }
        })
        return count;
    }
}
export  default app;

2、todolist案例實現

import React from ‘react‘;
import storage from ‘../modules/storage‘;
class Todolist1 extends React.Component{
    constructor(props){
        super(props);
        
 
this.state={
                list:[],
                finishList:[
                  /*  {
                        title:"錄制java",
                        checked:true
                    },
                    {
                        title:"錄制react",
                        checked:false
                    },
                    {
                        title:"錄制python",
                        checked:true
                    }*/
                ]
        };
    }

    //生命周期函數    頁面加載就會觸發
    componentDidMount(){
        //獲取緩存的數據
        let todoList = storage.get("TodoList");
        if(todoList){
            this.setState({
                finishList:todoList
            })
        }
    }
    addData=(e)=>{
        if(e.keyCode==13){
            let title=this.refs.title.value;
            let tempList = this.state.finishList;
            tempList.push({
                title:title,
                checked:false
            })
            this.setState({
                list:tempList
            });
            //增加框設置為空
            this.refs.title.value="";
            //緩存數據,使用localStorage，而將一個對象轉為字符串使用JSON.stringify()函數
            storage.set("TodoList",tempList);
        }
    }

    changeState=(key)=>{
        let templist =this.state.finishList;
        templist[key].checked =!templist[key].checked;
        this.setState({
            list:templist
        });
        storage.set("TodoList",templist);
    }
    deleteData=(key)=>{
        let templist =this.state.finishList;
        templist.splice(key,1);
        this.setState({
            list:templist
        })
        storage.set("TodoList",templist);
    }

    render(){
        return (
            <div>
                Todolist index
                <h2>Todolist演示</h2>
                <input ref="title" onKeyUp={this.addData}/>
                <hr/>
                <h2>

                </h2>
               <h2>正在進行</h2>

                <hr/>
                {
                    this.state.finishList.map( (value,key)=> {
                        if(value.checked==false){
                            return(
                                <li key={key}>
                                    <input type="checkbox" checked={value.checked} onChange={this.changeState.bind(this,key)}/>{value.title}
                                    ---<button onClick={this.deleteData.bind(this,key)}>刪除</button>
                                </li>
                            )
                        }
                    })
                }
                <h2>已完成事項</h2>
                {
                    this.state.finishList.map( (value,key)=> {
                        if(value.checked==true){
                            return(
                                <li key={key}>
                                    <input type="checkbox" checked={value.checked} onChange={this.changeState.bind(this,key)} />{value.title}
                                    ---<button onClick={this.deleteData.bind(this,key)}>刪除</button>
                                </li>
                            )
                        }
                    })
                }
                <hr/>



            </div>
        )
    }
}
export  default Todolist1;

3、app.js加載該組建

import React, { Component } from ‘react‘;
import ‘./assets/css/App.css‘;
import Todolist1 from ‘./components/Todolist1‘;
class App extends Component {
  render() {
    return(
        <div>
            你好
            <Todolist1/>
        </div>
    )
  }
}
export default App;

註意：

1、localStorage的使用
2、this對象的指向

react綜合案例-todolist、localstorage緩存數據