thenable

async.js

var ASYNC = {
   then: function then(o) {
        typeof o === 'function' ? o() : false;
        return {
          then : this.then,
          defer : this.defer
        }
   },
   defer: function then(o,t) {
       return new Promise(function(res,rej) {
	  setTimeout(function() {
            typeof o === 'function' ? o() : false;
            res(); 
          }.bind(this), t);
       }.bind(this));
   }
}

var b = Object.create(ASYNC);

b.then(function() {  console.log('a') }).then(function() { console.log('b') }).defer(function() { console.log('c') },3000).then(function() { console.log('d') }).then(function() { console.log('e') })