Detailed explanation of js/jquery parsing json method

This time I will bring you a detailed explanation of the js/jquery parsing json method. What are the precautions for js/jquery parsing json? The following is a practical case, let's take a look.

Before parsing, we must clarify several concepts: What are the differences and contact points between arrays, associative arrays and json?

1. Concept introduction1. Array

Syntax:
ECMAScript v3 specifies the syntax of array literals, JavaScript 1.2 and JScript 3.0 implement it. You can create and initialize an array by placing a comma-separated list of expressions in square brackets. The values ​​of these expressions will become array elements. For example:

var a = [1, true, 'abc'];

See API for specific operations.

ps: Must be separated by square brackets.

2. Associative array

1. Syntax:

var myhash= {”key1″:”val1″, “key2″:”val2″ };//obj

2.var

myhash= {key1:”val1″, key2:”val2″ };//obj-也可以

ps : Almost the same as the json format, but the json format requirements are more strict (the key-value pairs inside must use double quotes), but json can only be used as a format standard. If you want to operate on it, it must be converted into an associative array object (obj) .

2. Simple operation1. Add a key value to the Hash associative array

// 添加一个新键 newkey ，键值为 newval
myhash[”newkey”] = “newval”;

2. Delete the existing key value of the Hash associative 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 .Traverse the Hash associative array

// 遍历整个hash 数组 
for (key in myhash) {
val = myhash[key];
}

4.Get the value

Method 1.myhash.key1
Method 2.myhash.key2

##3.jsonFormat requirements:

{”key1″:”val1″, “key2″:”val2″ };//Strictly follow this format, and the operation can be based on the operation of the associative array

2. Several key points in front-end and back-end interactions1. When the data sent by the server is not one json, but multiple jsons, it should be assembled by contacting arrays and associative arraysStringFor example: var objs = [{ id: 1, name: 'n_1' }, { id: 2, name: 'n_2'}];

2. To the beginning In the end, the data provided by the server to the client is only a string, so in order to enable it to perform necessary operations on it in js, it can be converted into a js executable object through eval().

Therefore, the $.parseJSON() provided in jQuey has limitations. If it is the situation mentioned in 1 above, you must use eval() for conversion, and then pass $.each(objs,function(i ,o){...}) to operate

3. Specific example codePage code:

@Override
 protected void service(HttpServletRequest req, HttpServletResponse reps)
   throws Servlet
Exception
, 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();
 }

 @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();
 }

I believe I read the case in this article You have mastered the method. For more exciting information, please pay attention to other related articles on the php Chinese website!

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