ajax调用如何将数据返回到变量？

Question

function getMDBChanges(syncURL, LastSync, WSName, callback) {

    $.ajax({
           url: syncURL + WSName,
           dataType: "json",
           success: function (data) {
               callback(data);
           },
           error: function (model, response) {
               Notify("divNoteLeft","Nothing to be Sync'd from the Server with URL " + syncURL + WSName );
           }
    });

}

This is the code I am running. This works fine. But still I don't understand what exactly does the success callback does.
thank you

Answer 1

The success (and error ) callbacks are function references (they point to functions). When jQuery receives a success response to the AJAX request, it executes the function that the function reference points to, and passes it three arguments: the returned response (possibly with some pre-processing done on it based on the specified dataType), a status (as a string), and the jqXhr object that issued the request.

That's all it does: calls a function with some arguments; data is just the name of a parameter in a function definition, you could call that pretty much whatever you liked. It doesn't return any data to a variable.

Answer 2

In the callback,

function getMDBChanges(syncURL, LastSync, WSName, callback)

the function call might be a inner function in the callback area. For example,

getMDBChanges("www.xyz.com","21st April","WSName",function(data) {
   alert(data);
});

Answer 3

Wherever in your code you are calling the function getMDBChanges you are passing in a callback function which is I assume, processing the returned data. If you want to know what that function is add a console.log(callback); and you will see exactly what the function is and what it's doing.