Loading Modules in JavaScript v2

include.js

// $Revision: 5816 $

var include;
if (!include) { include = {}; }

include.base = ".";

include.ModuleLoader = function ModuleLoader() {
    this.loadingModules = {};
    this.loadedModules = {};
};

include.ModuleLoader.prototype.loadModule = function(module, cb) {
    if (this.loadedModules[module]) {
        cb();
        return;
    }

    if (!this.loadingModules[module]) {
        this.loadingModules[module] = [];

        this.addScriptTag(module);
    }
    if (cb) {
        this.loadingModules[module].push(cb);
    }
};

include.ModuleLoader.prototype.addScriptTag = function(module) {
    var scriptTag = document.createElement("script");
    scriptTag.setAttribute("lang", "javascript");
    scriptTag.setAttribute("type", "application/javascript");
    scriptTag.setAttribute("src", this.moduleNameToFilename(module));
    scriptTag.onerror = function() { throw("could not load module " + module); }
    document.getElementsByTagName("head")[0].appendChild(scriptTag);
};

include.ModuleLoader.prototype.moduleNameToFilename = function(module) {
    var prefix = include.base == "/" ? "/" : include.base + "/";
    return prefix + module.replace(/\./g, "/") + ".js";
};

include.ModuleLoader.prototype.moduleLoaded = function(module) {
    this.loadedModules[module] = true;
    for (var i = 0; i < this.loadingModules[module].length; i++) {
        this.loadingModules[module][i]();
    }
    delete this.loadingModules[module];
};

include.loader = new include.ModuleLoader();

include.module = function(module, cb) {
    include.loader.loadModule(module, cb);
};

include.moduleLoaded = function(module) {
    include.loader.moduleLoaded(module);
};