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HomeWeb Front-endH5 TutorialHTML5本地存储之Web Storage篇

Web Storage是HTML5引入的一个非常重要的功能,可以在客户端本地存储数据,类似HTML4的cookie,但可实现功能要比cookie强大的多,cookie大小被限制在4KB,Web Storage官方建议为每个网站5MB。


Web Storage又分为两种:

  • sessionStorage
  • localStorage


从字面意思就可以很清楚的看出来,sessionStorage将数据保存在session中,浏览器关闭也就没了;而localStorage则一直将数据保存在客户端本地;


不管是sessionStorage,还是localStorage,可使用的API都相同,常用的有如下几个(以localStorage为例):

  • 保存数据:localStorage.setItem(key,value);
  • 读取数据:localStorage.getItem(key);
  • 删除单个数据:localStorage.removeItem(key);
  • 删除所有数据:localStorage.clear();
  • 得到某个索引的key:localStorage.key(index);


如上,key和value都必须为字符串,换言之,web Storage的API只能操作字符串。


接下来,我们通过Web Storage开发一个简单的通讯录小程序,以演示相关API的使用方法;我们要实现如下功能:


  1. 录入联系人,联系人有姓名、手机号码2个字段,以手机号作为key存入localStorage;
  2. 根据手机号码,查找机主;
  3. 列出当前已保存的所有联系人信息;


首先,准备一个简单的HTML页面,如下:


[html] 
  1. nbsp;HTML>  
  2. html>  
  3. head>  
  4.     meta charset="utf-8"/>  
  5.     title>HTML5本地存储之Web Storage篇title>  
  6. head>  
  7. body>  
  8.     div style="border: 2px dashed #ccc;width:320px;text-align:center;">     
  9.         label for="user_name">姓名:label>  
  10.         input type="text" id="user_name" name="user_name" class="text"/>  
  11.         br/>  
  12.         label for="mobilephone">手机:label>  
  13.         input type="text" id="mobilephone" name="mobilephone"/>  
  14.         br/>  
  15.         input type="button" onclick="save()" value="新增记录"/>  
  16.         hr/>  
  17.         label for="search_phone">输入手机号:label>  
  18.         input type="text" id="search_phone" name="search_phone"/>  
  19.         input type="button" onclick="find()" value="查找机主"/>  
  20.         p id="find_result">br/>p>  
  21.     div>  
  22.     br/>  
  23.     div id="list">  
  24.     div>  
  25. body>  
  26. html>  

界面展现如下:

HTML5本地存储之Web Storage篇


要实现联系人的保存,只需要简单实现如下JS方法即可:

[javascript] 
  1. //保存数据   
  2. function save(){  
  3.     var mobilephone = document.getElementById("mobilephone").value;  
  4.     var user_name = document.getElementById("user_name").value;  
  5.     localStorage.setItem(mobilephone,user_name);  
  6. }  

要实现查找机主,则实现如下JS方法:

[javascript] 
  1. //查找数据   
  2. function find(){  
  3.     var search_phone = document.getElementById("search_phone").value;  
  4.     var name = localStorage.getItem(search_phone);  
  5.     var find_result = document.getElementById("find_result");  
  6.     find_result.innerHTML = search_phone + "的机主是:" + name;  
  7. }  


HTML5本地存储之Web Storage篇


要展现所有已保存的联系人信息,则需要使用localStorage.key(index)方法,如下:

[javascript] 
  1. //将所有存储在localStorage中的对象提取出来,并展现到界面上   
  2. function loadAll(){  
  3.     var list = document.getElementById("list");  
  4.     if(localStorage.length>0){  
  5.         var result = "";  
  6.         result += "
  7. ";  
  8.         for(var i=0;i
  9.             var mobilephone = localStorage.key(i);  
  10.             var name = localStorage.getItem(mobilephone);  
  11.             result += "
  12. ";  
  13.         }  
  14.         result += "
  15. 姓名 手机号码
    "+name+" "+mobilephone+"
    "
    ;  
  16.         list.innerHTML = result;  
  17.     }else{  
  18.         list.innerHTML = "目前数据为空,赶紧开始加入联系人吧";  
  19.     }  
  20. }  
"; result += ""; for(var i=0;i"; } result += "
姓名 手机号码
"+name+" "+mobilephone+"
"; list.innerHTML = result; }else{ list.innerHTML = "目前数据为空,赶紧开始加入联系人吧"; } }

效果如下:

HTML5本地存储之Web Storage篇


     问题:如上的演示,都只有2个字段,姓名和手机号码,如果要存入更为丰富的联系人信息,比如公司名称、家庭地址等,如何实现呢?Web Storage不是只能处理字符串吗?此时,可以利用JSON的stringify()方法,将复杂对象转变成字符串,存入Web Storage中;当从Web Storage中读取时,可以通过JSON的parse()方法再转换成JSON对象;


如下简单演示增加了公司属性的联系人保存JS代码:

[javascript] 
  1. //保存数据   
  2. function save(){  
  3.     var contact = new Object;  
  4.     contact.user_name = document.getElementById("user_name").value;  
  5.     contact.mobilephone = document.getElementById("mobilephone").value;  
  6.     contact.company = document.getElementById("company").value;  
  7.     var str = JSON.stringify(contact);  
  8.     localStorage.setItem(contact.mobilephone,str);  
  9.     loadAll();  
  10. }  
  11. //将所有存储在localStorage中的对象提取出来,并展现到界面上   
  12. function loadAll(){  
  13.     var list = document.getElementById("list");  
  14.     if(localStorage.length>0){  
  15.         var result = "";  
  16.         result += "
  17. ";  
  18.         for(var i=0;i
  19.             var mobilephone = localStorage.key(i);  
  20.             var str = localStorage.getItem(mobilephone);  
  21.             var contact = JSON.parse(str);  
  22.             result += "
  23. ";  
  24.         }  
  25.         result += "
  26. 姓名 手机 公司
    "+contact.user_name+" "+contact.mobilephone+" "+contact.company+"
    "
    ;  
  27.         list.innerHTML = result;  
  28.     }else{  
  29.         list.innerHTML = "目前数据为空,赶紧开始加入联系人吧";  
  30.     }  
  31. }  
"; result += ""; for(var i=0;i"; } result += "
姓名 手机 公司
"+contact.user_name+" "+contact.mobilephone+" "+contact.company+"
"; list.innerHTML = result; }else{ list.innerHTML = "目前数据为空,赶紧开始加入联系人吧"; } }

效果如下:

HTML5本地存储之Web Storage篇


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