An Object Lesson In JavaScript - Construction Crew (
Page 8 of 9 )
There are a couple of other interesting things about
JavaScript objects. For example, should you ever need to, you can obtain
complete information on an object's constructor via the "constructor" property.
The following example demonstrates how it can be used with the Sumthing object
constructor.
<script language="JavaScript">
alpha = new Sumthing(23, 865);
alert("The object constructor for alpha is " + alpha.constructor);
</script>
Here's what it looks like:
And you can use the "prototype" keyword to add new
object properties to an already existing object - consider the following
addition to the Room object you just saw:
<script language="JavaScript">
// Room object
// accepts area (sq. ft.) and colour (walls) as parameters
function Room(area, colour)
{
this.area = area;
this.colour = colour;
}
Room.prototype.direction = "east";
</script>
This would add an object property named "direction", with
value "east" to the Room object constructor. And when you try to access the
object property
<script language="JavaScript">
Kitchen = new Room(1000, "green");
alert(Kitchen.direction);
</script>
you should see this:
The
"prototype" keyword can be used to add object methods as well - try it yourself
and see!
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