Promise

var promise1 = new Promise(function(resolve, reject) {
  setTimeout(function() {
    console.log("I am resolving"); 
    resolve('foo');
  }, 300);
  console.log("Just inited me, not yet resolved");
});
var pro2 = Promise.resolve().then((val) => {
  console.log("Calling promise");
  return promise1.then(function(val1) {
    console.log("Promise was resolved and returned value");
    return val1 ;
  });
});
pro2.then((val) => {
  console.log(val);
});

Note: the then will be called right after the resolve is invoked