DOMReady.js

// Check if the DOM is ready every 100ms.
// If it is, clear the interval and do
// what you need to do inside the if statement
var isTheDomReady = setInterval(function() {
  if (document.readyState === 'complete') {
    clearInterval(isTheDomReady); // document ready, clear interval
    // Do your stuff here.
  }
}, 100);

// ES6
let isTheDomReady = setInterval(() => {
  if (document.readyState === 'complete') {
    clearInterval(isTheDomReady); // document ready, clear interval
    // Do  your stuff here.
  }
}, 100);