Dummy example to show why we write asychronous code LOL (http://jsfiddle.net/T9feW/)

demo.js

// See your dev console. Don't forget the reason you use promise
// is to write asynchronous code in synchronous way.
// We duplicate two instances of step1-3 whichever comes back first
// gets the counter = 1 and the latter one gets counter  = 2.
// The message "end of program let's quit" will print before
// any result comes back.
// Require Q.js (just go to jsfiddle)

var counter = 0;
function step1() {
    console.log("Executing step1 before returning a promise");
    return Q.delay(1000).then(function() {
        console.log("Returning from step1");
    });
}

function step2() {
    console.log("Executing step2 before returning a promise");
    return Q.delay(2000).then(function() {
        console.log("Returning from step2");
    });
}

function step3() {
    console.log("Executing step3 before returning a promise");
    return Q.delay(3000).then(function() {
        console.log("Returning from step3");
        counter += 1;
        console.log(counter);
    });
}

step1().then(step2).then(step3);
step1().then(step2).then(step3);
console.log("end of program let's quit");