Detailed explanation of simple implementation methods for converting JavaScript json objects and arrays

The difference between js array and json

1. Array

1. DefinitionOne-dimensional array: var s1=new Array();

            s1=[1,2,3,4] or s1[0]=1,s1[1]=2,s1[3]=3,s1[4]=4;
                                                                                                                                                                                                 through [0]);

The result is 1;

2,, define the two-dimensional prime group: var s1=new Array();

var s1= [[3,1],[2,3,4],3,[4,5,6,7,8]];
            alert(s1[1][0]);

                                                                                    The result is 2; json string

The so-called json string means that the value of the string variable has the same format as json, but is not a json object

Although the value of status_process conforms to the format of the json object, it Not an object, just a string (pieced together);

Convert the string to a json object

Use the function

eval, eval("(" + status_process+ ")");

Conclusion: What is passed from the background to the foreground is a json string, not a real json object, so it needs to be converted using the eval function.

Usage of json objects

var status_process = {
      " name5" : '闲置期',
    "name1" : '播种期',
    "name2" : '苗期',
    "name3" : '生长期',
    "name4" : '采收期'
   }   
  alert(status_process);

Both are: idle period

JSON syntax rules

JSON syntax is a subset of

JavaScript

object notation syntax. • Data is in name/value pairs • Data is separated by commas • Curly braces hold objects

• Square brackets hold arrays

JSON object

JSON object is written in curly braces:

The object can contain multiple name/value pairs:

var status_process = {
      name5 : '闲置期',
     name1 : '播种期',
     name2 : '苗期',
      name3 : '生长期',
      name4 : '采收期'
     };
     alert(status_process["name5"]);
     alert(status_process.name5);

This is also easy to understand , equivalent to this JavaScript statement:

{ "firstName":"John" , "lastName":"Doe" }

JSON array

JSON array is written in square brackets:

Array can contain multiple objects :

firstName = "John"
lastName = "Doe"

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

JSON file

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

•The MIME type of the JSON text is "application/ json"

Convert JSON text to JavaScript objectJavaScript function eval() can be used to convert JSON text to JavaScript object.

The eval() function uses the JavaScript compiler to parse JSON text and then generate JavaScript objects. The text must be enclosed in brackets to avoid

Syntax errors
:

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

Example:

{ 
"employees": [ 
{ "firstName":"John" , "lastName":"Doe" }, 
{ "firstName":"Anna" , "lastName":"Smith" }, 
{ "firstName":"Peter" , "lastName":"Jones" } 
] 
}

Creating objects through
JavaScript

Array

  $.ajax({
    type: 'POST',
    url: '../../caseHandler.ashx?action=GetCase&id=' + id.toString(), //url action是方法的名称
    data: "",
    dataType: "text", //可以是text，如果用text，返回的结果为字符串；如果需要json格式的，可以设置为json
    ContentType: "application/json; charset=utf-8",
    success: function (returnedData) {
      getMarkerFeature(eval("(" + returnedData+ ")"));
    },
    error: function (msg) {
      alert("访问失败："+ msg);
    }
  });

JavaScript ObjectTwo types of property access Methodobject.attribute

object["attribute"]For example:

var employees = [
{ "firstName":"Bill" , "lastName":"Gates" },
{ "firstName":"George" , "lastName":"Bush" },
{ "firstName":"Thomas" , "lastName": "Carter" }
];

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