How do I declare a namespace in JavaScript?
I like this:
var yourNamespace = {
foo: function() {
},
bar: function() {
}
};
...
yourNamespace.foo();
I use the approach found on the Enterprise jQuery site:
Here is their example showing how to declare private & public properties and functions. Everything is done as a self-executing anonymous function.
(function( skillet, $, undefined ) {
//Private Property
var isHot = true;
//Public Property
skillet.ingredient = "Bacon Strips";
//Public Method
skillet.fry = function() {
var oliveOil;
addItem( "\t\n Butter \n\t" );
addItem( oliveOil );
console.log( "Frying " + skillet.ingredient );
};
//Private Method
function addItem( item ) {
if ( item !== undefined ) {
console.log( "Adding " + $.trim(item) );
}
}
}( window.skillet = window.skillet || {}, jQuery ));
So if you want to access one of the public members you would just go skillet.fry()
or skillet.ingredients
.
What's really cool is that you can now extend the namespace using the exact same syntax.
//Adding new Functionality to the skillet
(function( skillet, $, undefined ) {
//Private Property
var amountOfGrease = "1 Cup";
//Public Method
skillet.toString = function() {
console.log( skillet.quantity + " " +
skillet.ingredient + " & " +
amountOfGrease + " of Grease" );
console.log( isHot ? "Hot" : "Cold" );
};
}( window.skillet = window.skillet || {}, jQuery ));
The third undefined
argument
The third,
undefined
argument is the source of the variable of valueundefined
. I'm not sure if it's still relevant today, but while working with older browsers / JavaScript standards (ecmascript 5, javascript < 1.8.5 ~ firefox 4), the global-scope variableundefined
is writable, so anyone could rewrite its value. The third argument (when not passed a value) creates a variable namedundefined
which is scoped to the namespace/function. Because no value was passed when you created the name space, it defaults to the valueundefined
.