js method to read and parse JSON data

JSON (JavaScript Object Notation) is a lightweight data exchange format that uses a completely language-independent text format and is an ideal data exchange format. At the same time, JSON is a JavaScript native format, which means that processing JSON data in JavaScript does not require any special API or toolkit.

This article is mainly a summary of JS operations on JSON.

In JSON, there are two structures: objects and arrays.

1. An object starts with "{" (left bracket) and ends with "}" (right bracket). Each "name" is followed by a ":" (colon); "name/value" pairs are separated by "," (comma). The name is enclosed in quotes; the value must be enclosed in parentheses if it is a string, but not if it is a numeric value. For example:

var o={"xlid":"cxh","xldigitid":123456,"topscore":2000,"topplaytime":"2009-08-20"}；

2. An array is an ordered collection of values. An array starts with "[" (left bracket) and ends with "]" (right bracket). Use "," (comma) to separate values.

For example:

var jsonranklist = [
    {"xlid":"cxh","xldigitid":123456,"topscore":2000,"topplaytime":"2009-08-20"},
    {"xlid":"zd","xldigitid":123456,"topscore":1500,"topplaytime":"2009-11-20"}
];

In order to process JSON data conveniently, JSON provides the json.js package, download address: http://www.json.org/json.js

In the data transmission process, json is passed in the form of text, that is, a string, and JS operates on JSON objects, so the conversion between JSON objects and JSON strings is the key. For example:

JSON string:

var str1 = '{ "name": "cxh", "sex": "man" }';
JSON对象:
var str2 = { "name": "cxh", "sex": "man" };

1. Convert JSON string to JSON object

To use the str1 above, you must use the following to convert it into a JSON object first :

//由JSON字符串转换为JSON对象
var obj = eval('(' + str + ')');

or

var obj = str.parseJSON(); //由JSON字符串转换为JSON对象

or

var obj = JSON.parse(str); //由JSON字符串转换为JSON对象

Then, you can read it like this:

Alert(obj.name);
Alert(obj.sex);

Pay special attention: if obj is originally a JSON object, Then after using the eval() function to convert (even if it is converted multiple times) it will still be a JSON object, but there will be questions after using the parseJSON() function to process it (a syntax exception will be thrown).

2. You can use toJSONString() or the global method JSON.stringify() to convert the JSON object into a JSON string.

For example:

var last=obj.toJSONString(); //将JSON对象转化为JSON字符

or

var last=JSON.stringify(obj); //将JSON对象转化为JSON字符
alert(last);

Data group

var str='[{"name":"cxh","sex":"man"},{"name":"cxh1","sex":"man1"}]';    
var obj = str.parseJSON();    
alert(obj[0].name)

Note:

Among the above methods, except eval( ) function comes with js, and many other methods come from the json.js package. The new version of JSON modifies the API and injects both JSON.stringify() and JSON.parse() methods into the built-in objects of Javascript. The former becomes Object.toJSONString(), and the latter becomes String. parseJSON(). If you are prompted that the toJSONString() and parseJSON() methods cannot be found, it means that your json package version is too low.

The above is a detailed explanation of how js reads and parses JSON data. I hope it can help everyone.

Related recommendations:

How to get an instance of the array length in a Json array using JS

Notes on converting strings to json

Detailed explanation of Python’s parsing of JSON

The above is the detailed content of js method to read and parse JSON data. For more information, please follow other related articles on the PHP Chinese website!