json syntax rules

The json syntax is a subset of the javascript object notation syntax.

•data in name/value pairs

•data are separated by commas

•Curly braces save objects

•square brackets save array

json object

The json object is written in curly braces:

An object can contain multiple name/value pairs:

{"firstname":"john", "lastname":"doe"}

This is easy to understand,Is equivalent to this javascript statement:


json array

The json array is written in square brackets:

An array can contain multiple objects:

{"firstname":"john", "lastname":"doe"},{"firstname":"anna", "lastname":"smith"},{"firstname":"peter", "lastname":"jones"}

In the example above,The object "employees" is an array containing three objects.Each object represents a record about someone (with first and last names).

json file

The file type of the json file is ".json"

The mime type of the json text is "application/json"

json text to javascript object

The javascript function eval () can be used to convert json text into a javascript object.

The eval () function uses a javascript compiler that parses json text and generates a javascript object. Text must be enclosed in parentheses,This will prevent syntax errors:

var obj=eval ("(" + jsontxt + ")");


 $.ajax ({
    type:"post",    url:"../../casehandler.ashx&action=getcase&id=" + id.tostring (), // url action is the method name
    data:"",    datatype:"text", // can be text, if text is used, the returned result is a string;
If you need json format, you can set it to json
    contenttype:"application/json;charset=utf-8",    success:function (returneddata) {
      getmarkerfeature (eval ("(" + returneddata + ")"));
    },    error:function (msg) {
      alert ("Access failed:" + msg);

Create object array via javascript

var employees=[
{"firstname":"bill", "lastname":"gates"},{"firstname":"george", "lastname":"bush"},{"firstname":"thomas", "lastname":"carter"}

Two ways to access javascript object properties


object ["attribute"]


var employees=[
{"firstname":"bill", "lastname":"gates"},{"firstname":"george", "lastname":"bush"},{"firstname":"thomas", "lastname":"carter"}
alert (employees [0] .lastname);// Method 1
alert (employees [0] ["lastname"]);// Method 2
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