json格式

json是一种与语言无关的数据交换的格式，作用：

使用ajax进行前后台数据交换

移动端与服务端的数据交换

1．Json的格式与解析

json有两种格式：

1）对象格式：{"key1":obj,"key2":obj,"key3":obj...}

2）数组/集合格式：[obj,obj,obj...]

例如：user对象用json数据格式表示

{"username":"zhangsan","age":28,"password":"123","addr":"北京"}

List<Product> 用json数据格式表示

[{"pid":"10","pname":"小米4C"},{},{}]

注意：对象格式和数组格式可以互相嵌套

注意：json的key是字符串 json的value是Object

json的解析：

json是js的原生内容，也就意味着js可以直接取出json对象中的数据

如下：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>insertBefore.html</title>
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
  </head>
  <body>
       <ul>
		 <li id="bj" name="beijing">北京</li>
	   </ul>
  </body>
  
  <script language="JavaScript">
 	/**
	 * 案例五
	 * {
	 *   "param1":"value1",
	 *   "param2":{},
	 *   "param3":[{key:value,key:value},{key:value,key:value}]
	 * }
	 *  
	 *  
	 */
	 
	 var json = {
			"key1":"value1",
			"key2":{"firstname":"张","lastname":"三丰","age":100},
			"key3":[
 		          	{"name":"小双","age":28,"addr":"扬州"},
 		          	{"name":"建宁","age":18,"addr":"紫禁城"},
 		          	{"name":"阿珂","age":10,"addr":"山西"},
 		          ]
	 };
	 
	 alert(json.key2.lastname);
	 
	 alert(json.key3[2].name);
	 
	 
  </script>
</html>