Javascript模块化布局:如何从一个模块中调用另一个模块中定义的函数?

以下是javascript应用程序的模块化布局示例.我想开始在工作中使用这种结构.我正在努力弄清它是如何工作的，需要了解如何从另一个模块调用一个模块中定义的函数?这肯定是布局JavaScript繁重应用程序的最佳选择吗?

Below is an example of a modular layout of a javascript application. I want to start using such a structure for my work. I am struggling to get my head round how it works and need to understand how to call a function that is defined in one module from a different module? Is this definitely the bet way to layout a JavaScript heavy application?

window.MainModule = (function($, win, doc, undefined) {
    var modules = {};

    // -- Create as many modules as you need ...
    modules["alerter"] = (function(){
        var someFunction = function(){ alert('I alert first'); };

        return { 
            init: someFunction
        };
    }());

    modules["alerter2"] = (function(){
        var someFunction = function(){ alert('I alert second'); };

        return { 
            init: someFunction
        };
    }());

    return { 
        init: function(){
            for (var key in modules){
                modules[key].init();
            }
        }
    };
}(jQuery, this, document));

$(window.MainModule.init);