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 The object
model of JavaScript
Before we start diving in
head first, lets just a close look at the object concept of JavaScript,
which will all tie in with accessing forms.
JavaScript is a language of objects, and
objects are something you should not be afraid of. A simple example of an
object is the document object, which allows us to access various aspects of
a document, such as background color, referrer etc. JavaScript contains many
objects, each representing one component of the web page.
Think of an object as a "tool" that contains properties and
methods, allowing it to do things. Lets use a typical example. In real life,
a car would be the object, the leather seats, power steering would be the
properties, and the car's ability to move around is the object's method. In
JavaScript, its just like that. However, properties of one object may itself
be another object, which in turn contains other properties. This is
important, and I will talk a little more about this. The below is the
JavaScript Object tree, which lists, in order, each object, and also, the
precedence of the objects.
The JavaScript Object Tree
IMPORTANT: THIS IMAGE WAS TAKEN FROM THE NETSCAPE
JAVASCRIPT AUTHORING GUIDE. FULL CREDIT FOR THE ABOVE IMAGE GOES THERE.
If you want to access something further down
below the tree from the object "window", you use the (dot) operator to
specify your choice. For example, if you want to write something to the
current document, you would do something like the following:
window.document.write("Hola") However, its important to understand that the "window" part is
omitted for most references. The reason why you could write
document.write("Hola")instead of
window.document.write("Hola")is
because JavaScript assumes you are talking about the current window. Lets
have a look at how form objects are accessed.
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