Christian Heilmann

Show love to the Module Pattern

Back in February 2006 I declared my love for the object literal explaining that it is a great way of making sure your scripts don’t interfere with others as all you expose to the world is a single object name. Instead of

function init(){}
function doStuff(){}
var myMessage = ‘oi, gerrof!’;

which might be easily overwritten you can use

myScript = {
init:function(){},
doStuff:function(){},
myMessage:’oi, gerrof!’
}

and this way make sure that they don’t get overwritten or overwrite other methods or variables. You can access them as myScript.init(), myScript.doStuff() and myScript.myMessage. I liked this idea so much I argued for a length of time with my technical editor at that time that I want my book to be based on this kind of scripting or not at all.

The only annoyance I had with this is that it still leads to rather big methods, as you have to use the long name for every call of variables inside the object. True, you can use this, but when you use event handling and you don’t use the scope correction of the YUI event you’ll use that for the element the event occured on.

myScript = {
init:function(){
this.doStuff();
},
doStuff:function(){},
myMessage:’oi, gerrof!’
}

Is therefore not necessarily possible, so you need to use:

myScript = {
init:function(){
myScript.doStuff();
},
doStuff:function(){},
myMessage:’oi, gerrof!’
}

This, in much more complex scripts, can lead to a lot of code and typing (unless you use an IDE) and just seems bloated. I had a lot of problems fitting object literal scripts into 80 character code templates for the book and magazine articles for example.

The solution to shorter code is once again a thing from the mad JavaScript scientist’s lab of Douglas Crockford called the Module Pattern. If you want a very detailed and good explanation of what it does in terms of OO sorcery, check out the easy to follow explanation of the Module Pattern by Eric Miraglia on the YUI blog.

What the Module Pattern does for me on top of that is that it keeps my code short. I only expose those methods as public that need to be and then I can call them inside the main object by name of the method and not by objectname.methodname.

myScript = {
massivelyLongVariableProbablyGerman:1,
thisIsReallyLong:function(n){},
doStuff:function(n){},
init:function(){
myScript.doStuff(myScript.massivelyLongVariableProbablyGerman);
myScript.thisIsReallyLong(myScript.massivelyLongVariableProbablyGerman);
}

}
myScript.init();

becomes

myScript = function(){
var massivelyLongVariableProbablyGerman = 1;
function thisIsReallyLong(n){};
function doStuff(n){};
return {
init:function(){
doStuff(massivelyLongVariableProbablyGerman);
thisIsReallyLong(massivelyLongVariableProbablyGerman);
}

};
}();
myScript.init();

However, there are two problems remaining: if you want to call one public method from another public method you’d still need to go either via the this route or by prepending the main object name:

myScript = function(){
var massivelyLongVariableProbablyGerman = 1;
function thisIsReallyLong(n){};
function doStuff(n){};
return {
init:function(){
doStuff(massivelyLongVariableProbablyGerman);
thisIsReallyLong(massivelyLongVariableProbablyGerman);

otherPublic() // MASSIVE FAIL!
this.otherPublic() // myScript.otherPublic() //

},
otherPublic:function(){
}

};
}();
myScript.init();>

The other problem is that I am not too happy about the return {} with all the public methods in it, it still looks a bit alien to me. Caridy Patiño offered a solution to that problem on the YUIblog by simply creating an object with a short name inside the main object that can act as a shortcut for public methods to call each other:

var myScript = function(){
var pub = {};
var massivelyLongVariableProbablyGerman = 1;
function thisIsReallyLong(n){};
function doStuff(n){};
pub.init = function(){
doStuff(massivelyLongVariableProbablyGerman);
thisIsReallyLong(massivelyLongVariableProbablyGerman);
pub.otherPublic();
};
pub.otherPublic = function(){
};
return pub;
}();
myScript.init();

This also saves me one level of indentation which means I can fit even more code in 80 characters. I will use that much more in earnest now.

UPDATE

If you like what you see here, take it up another notch with the revealing module pattern