JavaScript simple implementation of namespace effect _javascript skills

JavaScript native does not support namespaces and needs to be implemented in a workaround.

Namespaces are important when we create a JavaScript library, and we can encapsulate the fragmented JavaScript file (*.js) that makes up this JavaScript library in a namespace without having to define a global function or class. For example, a person who appears more than once in this section, we can encapsulate it in the appropriate namespace as part of the library:

Code 5-13:

Copy Code code as follows:

var com = {};
Com.anyjava = {};
Com.anyjava.Person = function (name) {
Private members
var _name = name;

Access device
This.getname = function () {
return _name;
};
This.setname = function (name) {
_name = name;
};
};
Prototype
Com.anyjava.Person.prototype = {
Eat:function () {
Alert (This.getname () + "is eating something.");
},
Sleep:function () {
Alert (This.getname () + "is sleeping.");
},
Walk:function () {
Alert (This.getname () + "is walking.");
}
};
var dirk = new Com.anyjava.Person ("Dirk");
Dirk.eat ();

From code 5-13, we get a namespace that matches the Java developer's habits and specify our command space path when instantiating the person object.

Here's a tip, if you're using a JavaScript library that someone else has developed and with a more complete namespace plan, you might be tired of writing a lengthy namespace every time. For example, you are using the JavaScript library I developed, under the Com.anyjava.control.ui namespace, there are a lot of extended UI controls you want to use, and I don't think you want to write many times var xxx = new Com.anyjava.control.ui.XXX (). By specifying the namespace alias, we can write less repetitive code, as shown in code 5-14, another way to instantiate person in code 5-13:

Code 5-14:

Copy Code code as follows:

var ns = Com.anyjava;
var dirk = new NS. Person ("Dirk");
Dirk.eat ();

The last thing I'm going to say is that you need to be aware of a problem when using namespaces. When writing a JavaScript library, most of the time namespace declaration statements may appear in multiple locations in a JavaScript file, or multiple JavaScript files appear. But the JavaScript language attribute is that the last declared variable overrides a variable of the same name declared earlier, which requires us to pay attention to the issue of repeated declarations, which means that each time a Namespace object is declared, it is advisable to determine whether the namespace object already exists, as shown in code 5-15:

Code 5-15:

Copy Code code as follows:

if (typeof Com.anyjava = = "undefined") var Com.anyjava = {};

So we can make sure that the "Com.anyjava" object is declared only once.