22 Objects

The various interface elements of a form are treated as objects - having properties
and methods which JavaScript can access or modify.

See the next tutorial for the standard object heirarchy of a browser page.

In code, an

ways to reference a form (window part can be optional)
- window.document.forms[index]  
- window.document.forms[ "name" ]  
- window.documents.forms.name
. window.document.name

Objects have properties and methods

Variables can be defined as an object type or as a ref
variables are objects - have properties and methods

X = myobject[ "property_name" ] = 6

object.property = "value"    // literal string or number

var MyVar = window.open( "hello.html" , "html_name" , "width=200,height=200" );    //variable can be made to refer to an object

x = object.method();  // shows how to use methods
    // note that the parentheses are required, even though the method has no arguments
    // the parentheses () provide a visual that a function/method is being used
x = x.toUpperCase();  // uses the variable method to change its case
x = x.fontcolor( 'red' );  // uses the variable method to change fontcolor

X = document.forms(0).elements(0).name
X = document.MyForm.MyText.name

you can add properties or methods at will
- property - simply assign
- methods   - create function first i.e., such as oldfunction
                   - myobj.newmethodname = oldfunction

you can create a new object of your own creation :
- define structure   function AnyObject (a,b,c) {
     this .a
     this .b
    }
- create instance  X = new AnyObject


Web Page Objects :
document
table
form
button
image
link


Built - in Objects
- string
- math
- date
- array
- option
- function

How to use objects in a window :
The first image in an HTML document is document.images[0]
the second is document.images[1], and so on.

If you want to know how many images are in a document, you can
find out by checking the length of the images array :
document.images.length.

On a web page with a form named "myform" , access the form with :
window.document.myform

On a web page with a form named "myform" , access the form with :
window.document.myform

Common Properties / Methods   ----------------------------------------------
methods are always followed by parenthesis, whether they have arguments or not
window
methods :
open     window.open( "URL" , "name" , "features" );
close    
blur
focus
properties :
status    window.status = "hello" ;

document
methods :
writeln   window.writeln( "test line of text" );     // add \n character
write     window.writeln( "test line of text" );     // does not add \n character
properties :  

array     
methods :
properties :
length    document.images.length    --  gives number of images in the document

date
methods :
getSeconds
getMinutes
getHours
properties :
length    document.images.length    --  gives number of images in the document

Sample .open usage
window.open( "URL" , "name" , "location,menubar" );
window.open( "URL" , "name" , "location=no,status=no" );
window.open( "URL" , "name" , "location,height=100,width=100" );