Creating classed in JavaScript
- by Renso
Goal:Creating class instances in JavaScript is not available since you define "classes" in js with object literals. In order to create classical classes like you would in c#, ruby, java, etc, with inheritance and instances.Rather than typical class definitions using object literals, js has a constructor function and the NEW operator that will allow you to new-up a class and optionally provide initial properties to initialize the new object with.The new operator changes the function's context and behavior of the return statement.var Person = function(name) { this.name = name;}; //Init the personvar dude= new Person("renso");//Validate the instanceassert(dude instanceof Person);When a constructor function is called with the new keyword, the context changes from global window to a new and empty context specific to the instance; "this" will refer in this case to the "dude" context.Here is class pattern that you will need to define your own CLASS emulation library:var Class = function() { var _class = function() { this.init.apply(this, arguments); }; _class.prototype.init = function(){}; return _class;}var Person a new Class();Person.prototype.init = function() {};var person = new Person;In order for the class emulator to support adding functions and properties to static classes as well as object instances of People, change the emulator:var Class = function() { var _class = function() { this.init.apply(this, arguments); }; _class.prototype.init = function(){}; _class.fn = _class.prototype; _class.fn.parent = _class; //adding class properties _class.extend = function(obj) { var extended = obj.extended; for(var i in obj) { _class[i] = obj[i]; }; if(extended) extended(_class); }; //adding new instances _class.include = function(obj) { var included = obj.included; for(var i in obj) { _class.fn[i] = obj[i]; }; if(included) included(_class); }; return _class;}Now you can use it to create and extend your own object instances://adding static functions to the class Personvar Person = new Class();Person.extend({ find: function(name) {/*....*/}, delete: function(id) {/*....*/},});//calling static function findvar person = Person.find('renso'); //adding properties and functions to the class' prototype so that they are available on instances of the class Personvar Person = new Class;Person.extend({ save: function(name) {/*....*/}, delete: function(id) {/*....*/}});var dude = new Person;//calling instance functiondude.save('renso');
