JSON的两种结构------对象结构 & 数组结构

var jsonObj =
{
    "键名1":值1,
    "键名2":值2,
    ……
    "键名n":值n
}

var arr =
[
    {
        "键名1":值1,
        "键名2":值2
    },
    {
        "键名3":值3,
        "键名4":值4
    },
    ……
]

var people =
  { "programmers": [
    { "firstName": "Brett", "lastName":"McLaughlin", "email": "brett@newInstance.com" },
    { "firstName": "Jason", "lastName":"Hunter", "email": "jason@servlets.com" },
    { "firstName": "Elliotte", "lastName":"Harold", "email": "elharo@macfaq.com" }
   ],
  "authors": [
    { "firstName": "Isaac", "lastName": "Asimov", "genre": "science fiction" },
    { "firstName": "Tad", "lastName": "Williams", "genre": "fantasy" },
    { "firstName": "Frank", "lastName": "Peretti", "genre": "christian fiction" }
   ],
  "musicians": [
    { "firstName": "Eric", "lastName": "Clapton", "instrument": "guitar" },
    { "firstName": "Sergei", "lastName": "Rachmaninoff", "instrument": "piano" }
   ]
  }

Read------people.programmers[0].lastName;  //McLaughlin
Alter------people.musicians[1].lastName = "Rachmaninov";
delete------delete people.musicians[1].lastName;

for in 遍历:
	var myObj = { "name":"Tadm博客", "alexa":10000, "site":"https://liuhongwei3.github.io/" };
	for (x in myObj) {
	    $("#demo").html += x + "<br>";
	}  
  // name alexa site

	for (x in myObj) {
	    $("#demo").html += myObj[x] + "<br>";
	}  
  // Tadm博客 10000 https://liuhongwei3.github.io/

JSON.parse() 方法将数据转换为 JavaScript 对象:
	var obj = JSON.parse('{ "name":"Tadm博客", "alexa":10000, "site":"https://liuhongwei3.github.io/" }');
	$("#demo").html = obj.name + "：" + obj.site;
  // Tadm博客:https://liuhongwei3.github.io/

JSON.stringify() 方法将 JavaScript 对象转换为字符串:
	var obj = JSON.stringify('{ "name":"Tadm博客", "alexa":10000, "site":"https://liuhongwei3.github.io/" }');
	$("#demo").html = myJSON;
  // {"name":"Tadm博客","alexa":10000,"site":"https://liuhongwei3.github.io/"}

JAVA-JSON:
	JSONObject obj = new JSONObject();
	obj.put("name", "foo");
	obj.put("num", new Integer(100));
	obj.put("balance", new Double(1000.21));
	obj.put("is_vip", new Boolean(true));
	System.out.print(obj);
  // {"balance": 1000.21, "num":100, "is_vip":true, "name":"foo"}

AJAX-JSON:
	xmlhttp.onreadystatechange=function()
	{
	    if (xmlhttp.readyState==4 && xmlhttp.status==200)
	    {
	        document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
	        var jsonObj = JSON.parse(http_request.responseText);
            // jsonObj 变量现在包含数组结构，可以通过 jsonObj.name 和 jsonObj.country 的方式访问
            document.getElementById("Name").innerHTML = jsonObj.name;
            document.getElementById("Country").innerHTML = jsonObj.country;
	    }
	}
	xmlhttp.open("GET","/try/ajax/ajax_info.txt",true);
	xmlhttp.send();

总结

JSON 指的是 JavaScript 对象表示法（JavaScript Object Notation），是纯文本。
JSON 是 JS 对象的字符串表示法，它使用文本表示一个 JS 对象的信息，本质是一个字符串。
JSON 可以将 JavaScript对象中表示的一组数据转换为字符串，然后就可以在函数之间轻松地传递这个字符串，或者在异步应用程序中将字符串从Web客户机传递给服务器端程序。