trash-slots/scriptloader.js

function ScriptLoader() {
    var self = this;
    this.scriptCache = [];
    this.loadingScripts = [];
    this.finishedCallback = function() {};
    this.isAlreadyLoaded = function(scriptPath) {
        return this.scriptCache.indexOf(scriptPath) != -1;
    };

    this.attach = function(scriptPath) {
        if(this.isAlreadyLoaded(scriptPath)) {
            return;
        }
        var domElement = document.createElement("script");
        domElement.src = scriptPath;
        domElement.type="text/javascript";
        domElement.async = true;
        domElement.addEventListener('load', function(event){
            if(self.loadingScripts.indexOf(scriptPath) != -1) {
                self.loadingScripts.splice(self.loadingScripts.indexOf(scriptPath), 1);
            }
            if(self.loadingScripts.length == 0) {
                self.finishedCallback();
            }
        });
        this.loadingScripts.push(scriptPath);
        document.getElementsByTagName("body")[0].appendChild(domElement);
        this.scriptCache.push(scriptPath);
    };

    this.finishedLoading = function(callback) {
        this.finishedCallback = callback;
    }
};
var loader = new ScriptLoader();
var include = function(scriptPath) {
    loader.attach(scriptPath);
};