Javascript Lazy loading

var scriptTag = document.createElement(‘script’);
scriptTag.src = ‘https://www.dropbox.com/static/api/2/dropins.js’; // set the src attribute
scriptTag.type = ‘text/javascript’; // if you have an HTML5 website you may want to comment this line out
scriptTag.async = true; // the HTML5 async attribute
scriptTag.id = ‘dropboxjs’; // the HTML5 Id
scriptTag.setAttribute(‘data-app-key’, ‘dropbox-key’) // Set Dropbox API key
var headTag = document.getElementsByTagName(‘head’)[0];
headTag.appendChild(scriptTag);