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This article mainly introduces the use of JSON in Ajax, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.

Although XML plays an important role in Ajax operation, JavaScript developers quickly lose interest in it. Manipulating XML in JavaScript has serious cross-browser problems, and extracting data from XML structures also involves traversing DOM documents, all of which require a lot of code. Douglas Crockford invented a data format called JSON (JavaScript Object Notation) but can create the same data structure as XML. JSON is based on a subset of JavaScript syntax, especially the literals of objects and arrays. JSON is designed to build formatted data on the server and then send it to the browser.

Because JSON is equivalent to objects and arrays in JavaScript, fast conversion speed, and easy to access in JavaScript code, JSON is more and more popular among developers in Ajax communication. The Web development community has developed JSON parsers and serializers for almost all major languages, making it extremely easy to output and use JSON data through the server.

Douglas Crockford also maintains a JSON serializer / parser for JavaScript, downloaded at http://www.json.org/js.html, to download the JavaScript file, which works in all browsers. In addition, the native version of the Crockford parser is included in IE8.

In the JSON library of Crockford, there is a global object that has two methods: parse () and stringify (). Where the parse () method takes two parameters: JSON text and an optional filter function. If the incoming text is a valid JSON, the parse () method returns an object representation of the incoming data. The following is an example of using the parse () method:

Var object=JSON.parse (())

Unlike using eval () directly, there is no need to put parentheses on the incoming text.

The second argument is a function that takes a JSON key and value as arguments. In order for the key passed as an argument to exit the existing result object, the function must return a value. Its return value will be the value associated with the specified key in the result object, so it gives us an opportunity to override the default parsing mechanism. In other words, if you return undefined for a key in this function, the key is removed from the result object. As shown in the following example:

Var jsontext= "{"\ name\ ":\" WangGang\ ",\" age\ ": 29,\" author\ ": true}"; var object=JSON.parse (jsontext,function (key,value) {switch (key) {case "age": return value+1; case "author": return undefined; default: return false;}}); alert (object.age) / / 30 alert (object.author) / / undefined

In the above code, the filter function adds 1 to the value of each "age" key, removes the "author" key from the data, and the other values are returned as is. As a result, the value of the age attribute in the resulting object becomes 30, but there is no author attribute, and this parsing function is often used to process the data returned by the server. Suppose addressbook.php returns JSON data in the following format:

{{"name": "WangMeng", "email": "wangmeng@some-domain-name.com"}, {"name": "LinTao", "email": "linTao@some-domain-name.com"}, {"name": "Jim", "email": "jim@some-domain-name.com"}}

You can send an Ajax request to get the above data, and then generate the corresponding elements on the client using the following code:

Var xhr=createXHR (); xhr.onreadystatechange=function () {if (xhr.readyState = = 4) {if ((xhr.status > = 200 & & xhr.status < 300) | | xhr.status = = 304) {var contacts=JSON.parse (xhr.responseText); var list=document.getElementById ("contacts"); for (var ionomer)

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