Deferred w/ a Promise

by someprimetime

JavaScript

function asyncEvent(){
    var dfd = new jQuery.Deferred();

    // Resolve after a random interval
    setTimeout(function(){
        dfd.resolve("hurray");
    }, Math.floor(400+Math.random()*2000));

    // Reject after a random interval
    setTimeout(function(){
        dfd.reject("sorry");
    }, Math.floor(400+Math.random()*2000));

    // Show a "working..." message every half-second
    setTimeout(function working(){
        if ( dfd.state() === "pending" ) {
            dfd.notify("working... ");
            setTimeout(working, 500);
        }
    }, 1);

    // Return the Promise so caller can't change the Deferred
    return dfd.promise();
}

// Attach a done, fail, and progress handler for the asyncEvent
$.when( asyncEvent() ).then(
    function(status){
        alert( status+', things are going well' );
    },
    function(status){
        alert( status+', you fail this time' );
    },
    function(status){
        $("body").append(status);
    }
);