simple-cls
a simple class system for node.js that adds a number of object-oriented features to the basic javascript language, including
- convinient class definition with inheritance
- abstract class a.k.a. interface support
- runtime introspection with dynamic type checking
The design goal is to provide a clean and easily understandable class system while minimizing overhead and avoid poluting the javascript built-in objects. It is inspired and built upon the defineClass from JavaScript The Definitive Guide.
Usage
Install the package "simple-cls"
npm install simple-cls
To define a class, do the following
var cls = require('simple-cls')
var MyClass = cls.defineClass({
//optional class name
name : "MyClass",
//optional super class, default is Object
extend : BaseClass,
//constructor code
construct : function(msg){
this.msg = msg;
},
//instance methods
methods: {
foo: function() {
console.log("foo");
}
},
//instance variables
variables: {
bar : 1,
msg : null
},
// class level variables or methods
statics : {
}
});
To instantiate an object and start using it
var obj = new MyClass("hello");
obj.foo();
console.log(obj.bar);
Concept
in simple-cls, the class system is built upon a chain of triple objects, namely the Prototype, Constructor and Class. As the diagram shows, instantiating a new js object will establish a relationship from the bottom up, starting at the object instance. Using javascript's built-in function we can obtain the prototype of that object.
assert.ok(Object.getPrototypeOf(obj) === MyClass.prototype);)
The prototype object itself is an object instance of the superclass of MyClass. If no superclass is given, it is defaulted to Object. MyClass is an alias of the Constructor function for obj
assert.ok(obj.constructor === MyClass)
The Class object contains runtime information about the obj class and can be obtained via __class on the constructor or .getClass() methods
assert.ok(obj.constructor.__class === obj.getClass())
To check if a js object is an instance of a class, or an instance of a subclass of some super classes
test.ok(obj.getClass().isKindOfClass('MyClass'));
test.ok(obj.getClass().isKindOfClass('BaseClass'));
test.ok(obj.getClass().isKindOfClass(MyClass.__class));
test.ok(obj.getClass().isKindOfClass(BaseClass.__class));
To look at all the methods callable from the obj, including methods defined on the super class
console.log(obj.getClass().getMethods());
For details, please look at the unit test examples.