inject script with tampermonkey

inject.js

// ==UserScript==
// @name         New Userscript
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        http://targetsite.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    console.log("asdf");
    (function(d, script) {
        script = d.createElement('script');
        script.type = 'text/javascript';
        script.async = true;
        script.onload = function(){
            // remote script has loaded
        };
        script.src = 'http://yoursite.com/script.js';
        d.getElementsByTagName('head')[0].appendChild(script);
    }(document));
    // Your code here...
})();