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");

Just to clarify your question, do you want the two alert's to show a different message? — phuzi, Oct 02 '13 at 07:02
yes I want to show different message and also want to understand .deferred — Jitender, Oct 02 '13 at 07:03

score 5 · Accepted Answer · edited May 23 '17 at 12:09

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

Here are a few links, worth reading :

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

score 2 · Answer 2 · answered Oct 02 '13 at 07:08

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"]);

answered Oct 02 '13 at 07:08

Michael Lorton

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Thanks for ur answer. I want to know the same result we can get without using .deferred so why .deferred is useful see http://jsfiddle.net/WLpBB/1/ – Jitender Oct 02 '13 at 07:15
This answer is missing is educational explanation. – mickmackusa Apr 29 '21 at 05:55

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

2 Answers2