Tuesday, February 27, 2007

Defining Methods

A method is a function associated with an object. You define a method the same way you define a standard function. Then you use the following syntax to associate the function with an existing object:

object.methodname = function_name

where object is an existing object, methodname is the name you are assigning to the method, and function_name is the name of the function.

You can then call the method in the context of the object as follows:


You can define methods for an object type by including a method definition in the object constructor function. For example, you could define a function that would format and display the properties of the previously-defined car objects; for example,

function displayCar() {
var result = "A Beautiful " + this.year + " " + this.make
+ " " + this.model;

where pretty_print is function to display a horizontal rule and a string. Notice the use of this to refer to the object to which the method belongs.

You can make this function a method of car by adding the statement

this.displayCar = displayCar;

to the object definition. So, the full definition of car would now look like

function car(make, model, year, owner) {
this.make = make;
this.model = model;
this.year = year;
this.owner = owner;
this.displayCar = displayCar;

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