Namespacing in Javascript can be achieved in following ways
1. Single global variables
2. Prefix namespacing
3. Object literal notation
4. Nested namespacing
5. Immediately-invoked Function
6. Expressions
7. Namespace injection
Lets go in detail..
Single Global Variables:
Here we define a single Global variable which holds all methods and properties of object.
Ex.
var myExApplication = (function () {
function(){
//...
},
return{
//...
}
})();
Disadvantage: There are high chances of conflicts same variable could be used in some other part of code.
Prefix Namespacing:
Here we select a unique prefix namespace we wish to use (in this example, myExApplication_) and then define any methods, variables, or other objects after the prefix as follows
Ex.
var myExApplication_propertyA = {};
var myExApplication_propertyB = {};
function myExApplication_myMethod(){
//...
}
Disadvantage: We may end up having huge number of global variables thus tough manageable code.
Object Literal Notation:
Here an object contains a collection of key-value pairs with a colon separating each pair of keys and values, where keys can also represent new namespaces.
Ex.
var myExConfig = { //myExConfig is a JSON object and it contains all methods and props.
language: "english",
defaults: {
enableGeolocation: true,
enableSharing: false,
maxPhotos: 20
},
theme: {
skin: "a",
toolbars: {
index: "ui-navigation-toolbar",
pages: "ui-custom-toolbar"
}
}
}
Nested Namespacing:
Its an extension of Object Literal notation where an object includes another object and which in turn may include another object and so on to achieve a more granular name spacing.
Ex.
var myApp = myApp || {};
myApp.routers = myApp.routers || {};
myApp.model = myApp.model || {};
myApp.model.special = myApp.model.special || {}
Immediately Invoked Function Expressions (IIFE)s
In IIFEs an unnamed function is immediately invoked after it’s been defined and a namespace is passed as a parameter to contained objects.
Ex.
var namespace = namespace || {};
// here a namespace object is passed as a function
// parameter, where we assign public methods and
// properties to it
(function( o ){
o.foo = "foo";
o.bar = function(){
return "bar";
};
})( namespace );
console.log( namespace );
Namespace Injection:
This is another variation on the IIFE in which we “inject” the methods and properties for a specific namespace from within a function wrapper using this as a namespace proxy
Ex.
var myApp = myApp || {};
myApp.utils = {};
(function () {
var val = 5;
this.getValue = function () {
return val;
};
this.setValue = function( newVal ) {
val = newVal;
}
// also introduce a new sub-namespace
this.tools = {};
}).apply( myApp.utils );
// inject new behaviour into the tools namespace
// which we defined via the utilities module
(function () {
this.diagnose = function(){
return "diagnosis";
}
}).apply( myApp.utils.tools );
Here we select a unique prefix namespace we wish to use (in this example, myExApplication_) and then define any methods, variables, or other objects after the prefix as follows
Ex.
var myExApplication_propertyA = {};
var myExApplication_propertyB = {};
function myExApplication_myMethod(){
//...
}
Disadvantage: We may end up having huge number of global variables thus tough manageable code.
Object Literal Notation:
Here an object contains a collection of key-value pairs with a colon separating each pair of keys and values, where keys can also represent new namespaces.
Ex.
var myExConfig = { //myExConfig is a JSON object and it contains all methods and props.
language: "english",
defaults: {
enableGeolocation: true,
enableSharing: false,
maxPhotos: 20
},
theme: {
skin: "a",
toolbars: {
index: "ui-navigation-toolbar",
pages: "ui-custom-toolbar"
}
}
}
Nested Namespacing:
Its an extension of Object Literal notation where an object includes another object and which in turn may include another object and so on to achieve a more granular name spacing.
Ex.
var myApp = myApp || {};
myApp.routers = myApp.routers || {};
myApp.model = myApp.model || {};
myApp.model.special = myApp.model.special || {}
Immediately Invoked Function Expressions (IIFE)s
In IIFEs an unnamed function is immediately invoked after it’s been defined and a namespace is passed as a parameter to contained objects.
Ex.
var namespace = namespace || {};
// here a namespace object is passed as a function
// parameter, where we assign public methods and
// properties to it
(function( o ){
o.foo = "foo";
o.bar = function(){
return "bar";
};
})( namespace );
console.log( namespace );
Namespace Injection:
This is another variation on the IIFE in which we “inject” the methods and properties for a specific namespace from within a function wrapper using this as a namespace proxy
Ex.
var myApp = myApp || {};
myApp.utils = {};
(function () {
var val = 5;
this.getValue = function () {
return val;
};
this.setValue = function( newVal ) {
val = newVal;
}
// also introduce a new sub-namespace
this.tools = {};
}).apply( myApp.utils );
// inject new behaviour into the tools namespace
// which we defined via the utilities module
(function () {
this.diagnose = function(){
return "diagnosis";
}
}).apply( myApp.utils.tools );
