javascript - How to convert nested setTimeouts to promises -

using rsvp.js or other promises/a+ implementation how can turn code like...

console.log('step 1'); settimeout(function() {   console.log('step 2');   settimeout(function() {     console.log('step 3');   }, 100); }, 300); 

into promises implementation?

create delay function returns promise , resolves after specified time elapses in settimeout, this

function delay(time) {     return new rsvp.promise(function (resolve) {         settimeout(resolve, time);     }); } 

and can invoke this

console.log("step 1"); delay(3000)     .then(function () {         console.log("step 2");         return delay(1000);     })     .then(function () {         console.log("step 3");     });