May 08, 2021 JSON
1. First, the concept of introduction
2. Second, several key points in the front background interaction
Before parsing, we have to figure out a few concepts: arrays, association arrays, and the differences and contact points between jason?
Grammar:
ECMAScript v3 specifies the syntax of array direct quantities, which JavaScript 1.2 and JScript 3.0 implement. Y
ou can place a list of expressions separated by commas in square brackets, create and initialize an array. T
he values of these expressions become array elements.
For example:
var a = [1, true, 'abc'];
How to view the API.
ps: Must be separated by square brackets.
2, the associated array
(1) Grammar:
var myhash= {”key1″:”val1″, “key2″:”val2″ };//obj（2）var
myhash= {key1:”val1″, key2:”val2″ };//obj-也可以ps: It's almost the same as the jason format, but the jason format is more restrictive (the key pairs inside must use double quotes), but jason can only be used as a format standard and must be converted to an associated array object (obj) if you want to manipulate it.
2, simple operation
(1) Add key values to the Hash association array
// 添加一个新键 newkey ，键值为 newval
myhash[”newkey”] = “newval”;(2) Remove the key value of the hash association array
// 删除一个键 newkey ，同时，该键值对应的 newval 也就消失了
delete myhash[”newkey”];(3) Traversing the hash association array
// 遍历整个hash 数组
for (key in myhash) {
val = myhash[key];
}
（4）获得值
方式1.myhash.key1
方式2.myhash.key2
3、json
Format requirements:
"key1": "val1", "key2": "val2";
2. The data that the server gives to the client from start to finish is just a string, so in order for it to be able to do what is necessary in js, it can be converted to a js executable object by eval().
So the $.parseJSON() provided in jQuey is limited, and if this is the case mentioned in 1 above, it must be converted using eval() and then through $.each (objs, function (i, o)
Take action
Page code:
The code is as follows:
<body>
<input type="button" value="send ajax json" onclick="sendAjaxByjson();"/>
<input type="button" value="send ajax array" onclick="sendAjaxByarray();"/>
</body> <script type="text/javascript">
function sendAjaxByjson(){
$.post("json",{},function(data){
var obj=data;
alert(typeof obj);//string
//var a=eval(obj);不解，不注释则会报错..
var strToobj=$.parseJSON(obj);
alert(strToobj.name);
alert(typeof strToobj)//obj
var obja={'name':'techbirds','age':'23','sex':'male'};
alert(typeof obja);//obj
alert(obja['name']+":"+obja.age);
delete obja['name'];
});
}
function sendAjaxByarray(){
$.post("array",{},function(data){
var str=data;
alert(typeof str);//string
alert(typeof eval(str));//object
var obja=[1,2,3,4,5];
alert(typeof obja);//object
});
}
</script>
Background code:
The code is as follows:
@Override
protected void service(HttpServletRequest req, HttpServletResponse reps)
throws ServletException, IOException {
Map<String, Object> jsonMap=new HashMap<String, Object>();
jsonMap.put("name", "techbirds");
jsonMap.put("age", 23);
jsonMap.put("sex", "male");
reps.getWriter().print(JSONObject.fromObject(jsonMap).toString());
reps.getWriter().flush();
reps.getWriter().close();
}The code is as follows:
@Override
protected void service(HttpServletRequest req, HttpServletResponse reps)
throws ServletException, IOException {
String array="[1,2,3,4,5,6]";
reps.getWriter().print(array);
reps.getWriter().flush();
reps.getWriter().close();
}A johnson string for an array of json objects:
var str=[{"Price":12,"Name":"aaa","Age",22},{"Price":24,"Name":"bbb","Age",33}];In the fore desk, the parseJSON method of jquery is used for parsing, and the method of jquery's foreach is used for parsing, the code is as follows:
var jsonarray= $.parseJSON(str);
alert(jsonarray);
$.each(jsonarray, function (i, n)
{
alert(n.Price);
}var jsonarray= $.parseJSON(str);
$.each(eval("(" + jsonarray+ ")"), function (i, n) {
alert(n.Price);
}