Slide 15.26: JavaScript objects

JavaScript Objects

JavaScript is an object oriented programming language, which includes the following two features:

Properties are the values associated with an object.
Methods are the actions that can be performed on objects.

The code creates an instance of an object and adds two properties and one method to it. Note that methods are just functions attached to objects. Then we will have to write the createID function, which creates an ID for the customer. JavaScript knows which person you’re talking about by using this. So, now you can use the method user.createID. The example creates an object by using a template. You may also use the Object type to create an object.

The new operator creates an instance of a user-defined object type or of one of the built-in object types that has a constructor function.

The method random of the object Math returns a pseudo-random number between 0 and 1.

The String converts the specified object to a string. It is a top-level function and is not associated with any object.

Demonstration
The following demonstration shows how the script of HTML and JavaScript is displayed on the Web.


<html> <body> <script type="text/javascript"> function person( firstname, lastname, age, eyecolor) { this.firstname = firstname; this.lastname = lastname; this.age = age; this.eyecolor = eyecolor; } myFather = new person( "John", "Doe", 50, "blue" ); document.write( myFather.firstname + " is " + myFather.age + " years old." ); </script> </body> </html>