load popcorn dynamically

gistfile1.js

// load popcorn dynamically
var script = document.createElement("script");
script.type = "text/javascript";
script.src = '/static/js/popcorn.js';
document.getElementsByTagName("head")[0].appendChild(script);

function popcornReady() {
    // this is called when script loaded, but before Popcorn global ready
    console.log("popcorn ready callback");
    // console.log(Popcorn);
    }
script.onreadystatechange= function () {
    if (this.readyState == 'complete') popcornReady();
}

// this also does not work:
script.onload= popcornReady();

window.onload = function() {
  //Popcorn is only now available
}