The Promise in jquery

Reference http://www.ruanyifeng.com/blog/2011/08/a_detailed_explanation_of_jquery_deferred_object.html

The Ajax method has been rewritten since the jQuery1.5 version, not the same as it used to be. Now $.ajax () will return a Promise/deffered object

This object has the Do () fail () always () and then () Promise () reject () methods

I used to write Ajax like this,

$.ajax ({

URL: "Test.html",

Success:function () {

Alert ("Haha, success!") ");

},

Error:function () {

Alert ("Error! ");

}

});

Now it is

$.ajax ({

URL: '/path/to/file ',

Type: ' Default GET (other Values:post) ',

DataType: ' Default:intelligent Guess (other values:xml, JSON, script, or HTML) ',

Data: {param1: ' value1 '},

}). Done (function () {

Console.log ("Success");

}). Fail (function () {

Console.log ("error");

}). Always (function () {

Console.log ("complete");

});

Obviously, done () is equivalent to success () fail () is the error ()

Or

$.ajax ({

URL: ' Test1.json ',

DataType: ' Text ',

}). Then (function (res) {

Alert (' Wahha ');

Console.log (RES);

});

You can use the same callback for different requests

$.when ($.ajax ({

URL: ' Test1.json ',

DataType: ' Text ',

}), $.ajax ({

URL: ' Test2.json ',

DataType: ' Text ',

}). Done (function (res) {

Alert (' Wahha both ');

Console.log (res);//response of the first AJAX request

})

Add a callback function for a normal function

This is the most recommended way

var wait = function (DTD) {

var DTD = $. Deferred (); Inside the function, create a new deferred object

var tasks = function () {

Alert ("Execution finished!") ");

Dtd.resolve (); Change the execution state of the deferred object resolve to resolve

};

SetTimeout (tasks,5000);

return Dtd.promise (); Returns the Promise Object

};

$.when (Wait ())

. Done (function () {alert ("Haha, success! "); })

. Fail (function () {alert ("Error! "); });

The source post was previously a $. Deferred () as a global object, but that can change the state of execution in the global.

So he used the deferred.promise ()

The last thing I did was to put deferred in the function and solve the problem.

So later, multiple nested AJAX requests can be written like this

var Promisea = $.get (Urla);

Promisea.always (Donefna, Failfna, Progressfna);

var promiseb = Promisea.then (function () {

Return $.get (URLB);

});

Promiseb.always (DONEFNB, FAILFNB, PROGRESSFNB);

The Promise in jquery