promise.js

let myFirstPromise = new Promise((resolve, reject) => {
  // We call resolve(...) when what we were doing async succeeded, and reject(...) when it failed.
  // In this example, we use setTimeout(...) to simulate async code. 
  // In reality, you will probably be using something like XHR or an HTML5 API.
  setTimeout(function(){
    resolve("Good To go"); // Yay! Everything went well!
  }, 1000);
});

myFirstPromise.then((response) => {
  // successMessage is whatever we passed in the resolve(...) function above.
  // It doesn't have to be a string, but if it is only a succeed message, it probably will be.
  console.log(response);
});