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Showing posts from October, 2013

JavaScript - An Example for Inheritance

Everyone of us know, Inheritance is a way to acquire properties and methods of another object. In other words it is a way to establish is-a relationship between two objects. The static languages by default provide some easier ways to achieve this. For an example, we have "extend" keyword in Java for extending other object.
JavaScript is protypal inheritance language (class-free) means that objects can inherit properties from other objects. Let's see an example.

Let's create a parent class for Animal
/** * Animal - Constructor and parent class for all animals. * @param {Object} aType - Type of the animal * @param {Object} aName - Name of the animal */ function Animal(aType, aName) { this.type = aType; this.name = aName; } Animal.prototype.eat = function() { console.log('All animal will eat'); };
We have to do following steps for extending animal class.

1. Calling super class constructor from child class constructor.
2. Setting up prototype chain.
3.…

JavaScript - An example for Singleton pattern

The singleton pattern is a design pattern that restricts instantiation of the class to one object. This pattern is very handy when one object is enough for doing some operation across the entire system. Let's see an example.

/** * Single global namespace for an entire application with lazy loading. * @Singleton pattern */ var PUS = PUS || {}; PUS = (function(){ //Private variables and methods var appVersion = 0.1, instance = null; function constructor() { console.log('Object has created'); return { getAppVersion : function() { return appVersion; } }; }; return { getInstance : function() { if(!instance) { instance = constructor(); } return instance; } }; })();
Here PUS object contains one public method called "getInstance". If we call PUS. getInstance() method, that will first check whether an object is already created or not. The object is already exists then will return the reference of an existing object, otherw…

Static members in JavaScript

JavaScript static variables and methods are associated with the class, rather than with any object(similar to Java). Every instance of the same class has access to static members and rights to modify the values and method behavior at run-time. Let's see an example.

var Person = function(fName, lName) { this.firstName = fName; this.lastName = lName; Person.objectCounts++; }; //Static variable. Person.objectCounts = 0; //Static method. Person.getObjectInformation = function() { return Person.objectCounts; };
Here the variable objectCounts is a static variable and getObjectInformation is a static method. If we create any object for Person class, the static variable "objectCounts" value is incremented by one. The method getObjectInformation is used for getting "objectCounts" value.
var person1 = new Person('Suriya', 'A'); var person2 = new Person('John', 'H');
Here there are two objects created for Person class. Let's try to …