lamd: Simple and fast module handling for a bundled library

Building websites and dashboards can sometimes mean you can relax a little bit when it comes to the number of requests you make, cache headers and transfer time of assets. When it comes to delivering scripts to client pages at Kiosked, time is of the essence. There's no room to request extra assets of scripts from the server, because there's a good chance a user may have moved on before another request makes it back. To improve the user experience and ad revenue, we need to get the script to the client in one go in as small a space as possible.

Kiosked's library is a decent collection of scripts that perform different tasks, but they're delivered collectively to the client, so there's no need to request them separately. There is a need, however, to manage the scripts (modules) separately so that they can neatly address and require each other.

Originally, many moons ago, the entire system was namespaced in a very global fashion. This meant that things were easy to find, easy to lookup through the IDE and speedy because there were no function calls to define them. Ultimately, however, this made for a very poor design for several reasons:

  • Namespaced items are not minified - They're treated as API methods and are not converted into smaller names when run through minifiers like Google's Closure Compiler.
  • Namespaced items that extend others need to be loaded in a specific order. If class A extends B, B needs to preceed A in the bundled result. This means using something like grunt-scantree-concat (based off of scantree by getify) to 'require' each file to preceed one other, like

     // require: source/B.js
    
     var A = B.extend(function() { // ...
    
  • Writing names of classes and tools becomes ridiculous, especially when using locator patterns: GlobalNamespace.SpecialClassLocator.getSpecialClass().notifyChildren(data);.
  • Most class and utility code is exposed to the window, which is unnecessary and somewhat of a security concern.

To address these issues, I wrote a couple of different module loaders before sitting down at home and writing what I've now published as lamd. I really like the AMD style of module handling, and I wanted to use something like that at Kiosked. Most implementations I found online were either licensed incorrectly (or not at all), or contained a substantial amount of extra code for making remote requests (which we'd never do). Instead of trying to make one of those work, I did what you normally shouldn't do (if possible) and reinvented the wheel (albeit for a more specialised purpose).

lamd provides 2 methods, require and define, to the current script (var) (if require is not already defined) as those names respectively. It also sets lamd in the current script to an object:

lamd.define();
lamd.require();

require and define work much the same as their cousins in AMD.js or RequireJS.

require takes two parameters: require(ids, callback):

  • ids is a String or an Array of strings. This holds the ids of the modules you require for the callback function.
  • callback is a Function to run after the requirements are met. Each requirement is passed into the callback function as a parameter, in order.

define takes two or three parameters, depending on if it has dependencies: define(id, [dependencies,] callback):

  • id is a String, which is the name of the new module.
  • dependencies is an optional Array of strings for the dependencies of the module.
  • callback is Function or other non-undefined value. callback is called with the required modules, in order. callback must resolve to a value other than undefined, or an exception will be thrown.

For example:

require(["Person", "toolkit"], function(Person, toolkit) {
    var people = [
            new Person("Bob"),
            new Person("Fred")
        ],
        favouritePeople = people.filter(toolkit.peopleNamedBob);
    console.log(favouritePeople);
});

define("Person", function() {
    var Person = function(name) {
        this.name = name;
    };
    return Person;
});

define("toolkit", function() {
    return {
        peopleNamedBob: function(person) {
            return (person.name === "Bob");
        }
    };
});

Under the hood

Little lamd uses Promises underneath it all. Promises allow it to wait, at rest, or dependencies to be defined. There are no intervals or timeouts. Using native Promises is preferred, but if polyfilling, ensure you use a fill that supports setImmediate (for performance reasons).

lamd is designed for browser use, but would work in Node also (though I see absolutely no reason why you would want it to).