using-promise-es5.js

function printAfterTimeout(string, timeout, done){
  setTimeout(function(){
    done(string);
  }, timeout);
}

printAfterTimeout('Hello ', 2e3, function(result){
  console.log(result);
  // nested callback
  printAfterTimeout(result + 'Reader', 2e3, function(result){
    console.log(result);
  });
});
// Hello
// Hello Reader