You can user the RequireJS library.
To use it, simply download it and include it in your index.html, replacing static / js with the folder where your javascripts are:
<script data-main="static/js/main" src="static/js/require.js"></script>
In this example, there would be one main.js file, which would be responsible for importing all other files, using RequireJS.
So you should import your example.js file into main.js:
// main.js
require(['exemplo'], function() {
});
In the file where you need the external javascript, you should do something like this:
// exemplo.js
require(['http://360popunder.com/5feaf8db752a6f16f5f860f0bc7c60.js?wkid=xxx&wid=xxx&k=xxx&traffic=0&cap=10&cid=downloads', 'outro_arquivo_necessário'], function(){
// Toda sua lógica aqui dentro
});
Any question, or if it does not work for you, you can leave a comment that we try to find out why.
I suggest you read the RequireJS documentation if you choose to use it.