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Add()ing Some More - JavaScript

Think JavaScript is only good for image swaps and flying <div>s?Think again - this article takes an in-depth look at some of theobject-oriented constructs available in JavaScript, and demonstrates howJavaScript objects can substantially speed up code development anddeployment.

TABLE OF CONTENTS:
  1. An Object Lesson In JavaScript
  2. Object Lessons
  3. Sumthing New
  4. Alpha Radiation
  5. Add()ing Some More
  6. Turning Up The Heat
  7. Room With A View
  8. Construction Crew
  9. A Hot Date
By: Vikram Vaswani, (c) Melonfire
Rating: starstarstarstarstar / 23
April 02, 2001

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Just as you can define object properties, it's also possible to define object methods - essentially, simple JavaScript functions. A little more evolution, and the Sumthing object now sports an Add() method, which adds the values stored in "alpha" and "beta".
<script language="JavaScript">
// object constructor
function Sumthing(num1, num2) {
// object properties
this.alpha = num1;
this.beta = num2;
// object methods
this.Add = Add;
}
// object method Add() - add arguments
function Add() {
sum = this.alpha + this.beta;
return sum;
}
</script>

A couple of interesting things here. First, the object method Add() is actually defined outside the object constructor block, though it references object properties using the "this" keyword. And second, just as object properties are defined using "this", object methods need to be defined in the same manner - witness my addition of
function Sumthing(num1, num2) {
...
// object methods
this.Add = Add;
...
}

to the object constructor block.

Wanna see how it works? Take a look at the code
<script language="JavaScript">
obj = new Sumthing(2, 89);
alert("The sum of " + obj.alpha + " and " + obj.beta + " is " + obj.Add());
</script>

and the output.



And now that your object constructor is all ready to go, let's see a quick demonstration of how you can use it to spawn multiple instances of the same object, each operating independently of the other.
<script language="JavaScript">
// one object
obj1 = new Sumthing(2, 89);
alert("The sum of " + obj1.alpha + " and " + obj1.beta + " is " +
obj1.Add());
// another one
obj2 = new Sumthing(546, 67);
alert("The sum of " + obj2.alpha + " and " + obj2.beta + " is " +
obj2.Add());
// and a third one
obj3 = new Sumthing(2364237, 283457);
alert("The sum of " + obj3.alpha + " and " + obj3.beta + " is " +
obj3.Add());
</script>

Now *that* is cool!

 
 
>>> More JavaScript Articles          >>> More By Vikram Vaswani, (c) Melonfire
 

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