JavaScript操作localStorage实现保存本地json文件

/***************** 操作本地文件 *****************/
        //保存图书本地json
        function SaveLocalJson(data){
            localStorage.setItem("MyBook",data);
        }
        
        //查询所有保存本地json
        function GetLocalJson(){
            var readtext=localStorage.getItem("MyBook");
            var readJson=JSON.parse(readtext);
            return readJson;
        }
        
        
        //更新小说最后阅读的章节Id
        function UpdateLocalLastRead(novelId,lastReadId){
            var readtext=localStorage.getItem("MyBook");
            var readJson=JSON.parse(readtext);
            var count = Object.keys(readJson).length; 
            for(i=0;i<count;i++)
            {
                if(readJson[i].NovelId==novelId){
                    readJson[i].LastReadId=lastReadId;
                }
            }
            var jsontext= JSON.stringify(readJson);
            SaveLocalJson(jsontext);
        }
        
        //删除本地保存图书
        function RemoveMyBook(){
            localStorage.removeItem("MyBook");
        }
        /***************** end *****************/

		//创建localStorage对象
        var storage=window.localStorage;
        //创建数组
        var  persons = [];
        //存入对象
        persons.push({"name":"张三",age:23,'gender':true});
        persons.push({"name":"李四",age:23,'gender':true});
        persons.push({"name":"王五",age:23,'gender':true});
        //将个人信息用json的方法转换为字符串
        var s = JSON.stringify(persons);
        storage.setItem("message",s);

        //取出个人信息
        var json = localStorage.getItem("message")
        //将个人信息从一个字符串中解析出json对象
        var jsonObj = JSON.parse(json);
        console.log(json);
        /*[{"name":"张三","age":23,"gender":true},
        {"name":"李四","age":23,"gender":true},
        {"name":"王五","age":23,"gender":true}]*/
        for (var i =  0 ; i < jsonObj.length ; i++){
            console.log(jsonObj[i]);
            /*{name: "张三", age: 23, gender: true}
            {name: "李四", age: 23, gender: true}
            {name: "王五", age: 23, gender: true}*/
            var person = jsonObj[i];
            for (var message in person){
                console.log(person[message])
                /*张三
                  23
                  true*/
            }
        }

if(window.localStorage) { 
 // localStorge可用 
 }else { 
// localStorge不可用 
 } 

// 获取本地存储对象 
var localStorage =window.localStorage; 
// 存储 
localStorage.setItem("key",content); 

var myKey =localStorage.getItem("key"); 

localStorage.removeItem("key"); 

localStorage.clear(); 

// 定义json变量 
var json ={username:"杨朝来",sex:1,age:25,birthday:"1990-08-21",phonenumber:13812345678,disease:"肺小结节",insurance:1,avatar:"images/male.png"}; 
// json变量转化成json字符串 
var jsonstr =JSON.stringify(json); 
// 存储json字符串 
window.localStorage.setItem("jsonkey",jsonstr); 
// 取出json字符串 
var jsonstr =window.localStorage.getItem("jsonkey"); 
// 还原json对象 
var json =JSON.parse(jsonstr); 
// 取出json里面的username 
var username =json.username;