What is $.Deferred() and .resolve in jquery

Question

What exactly .deferred do what is its work and where and when we should use .deferred with resolve. In below function I have two .done callbacks. I want to set two different callback msg. fiddle

var deferred = $.Deferred();
deferred.done(function(value) {
    alert(value);
}).done(function(id){
alert(id)
});

console.log(deferred)

deferred.resolve("hello world");

Answer 1

jQuery.Deferred is the main tool of jQuery's implementation of the promise pattern.

Here are a few links, worth reading :

• [SO] Implement promises pattern
• [jQuery doc] Deferred
• [wikipedia] Futures and Promises

As for your specific need : you should use .then() (read the docs for .done() and .then()).

var deferred = $.Deferred();

deferred.then(function(value) {
    alert(value);
    return 42;
}).then(function(id){
    alert('The answer : ' + id);
});

console.log(deferred)

deferred.resolve("hello world");

fiddle

Answer 2

Would this do what you want?

var deferred = $.Deferred();
deferred.done(function(value) {
    alert(value[0]);
}).done(function(value){
    alert(value[1]);
});


deferred.resolve(["hello world", "goodbye, cruel world"]);