JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="doSomething()">
  Click me
</button>
<div id="response">
  Nothing happening yet
</div>

JavaScript

function myFirstFunction(event) {
  document.getElementById('response').innerHTML = "First function...";
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve('success');
      //reject('error');
    }, 2000);
  });

}

function followupFunction() {
  document.getElementById('response').innerHTML = "finished!";
}

function doSomething(event) {
  document.getElementById('response').innerHTML = "doing something...";
  return myFirstFunction(event).then(followupFunction);
};