pong-ml/js/autoload.js

var pendingClasses = [];
var loadedClasses = [];
var autoloader = (classname) => {
	pendingClasses.push(classname);
	return new Promise((resolve, reject) => {
		if(loadedClasses.indexOf(classname) != -1) {
			pendingClasses.splice(pendingClasses.indexOf(classname), 1);
			resolve(window[classname]);
		}
		
		let url = `./js/${classname}.js`;
		let script = document.createElement("script");
		script.src = url;
		script.type = "text/javascript";
		script.async = true;
		script.addEventListener('load', (event) => {
			pendingClasses.splice(pendingClasses.indexOf(classname), 1);
			loadedClasses.push(classname);
			resolve();
		});
		script.addEventListener('error', () => {
	    	reject(new Error(`Unable to load ${classname}: attempted location ${url}`));
	    });
		document.getElementsByTagName("body")[0].appendChild(script);
	});
};

var require = (classname) => {	
	autoloader(classname).then((classname) => {
		let event = new CustomEvent("JSScriptLoaded", {classname: classname});
		document.dispatchEvent(event);
	}).catch((e) => {
		console.error(e);
	});
};

document.addEventListener("JSScriptLoaded", (event) => {
	if(pendingClasses.length <= 0) {
		let event = new CustomEvent("JSContentLoaded", {classes: loadedClasses});
		document.dispatchEvent(event);
	}
});