[OCLUG-devel] Javascript - Overriding method definition

[Morgan Simpson]

Doug Jolley wrote:

> I have the following:
> 
> function purchase(description,price) {
> this.description=description;
> this.price=price;
> this.quantity=0;
> this.buttonStatus="add";
> this.amount=amount;
> }
> function amount() {
>    return parseFloat((this.quantity * this.price)+'');
> }
> 
> I then use a loop to populate an array with various purchase objects.
> Typically, there would be some number like say 20 different purchase
> objects contained in such an array.  As you can see, the amount of
> each purchase is simply quantity*price.  However, for sake of example,
> let's say that the 5th purchase object has a graduated pricing
> structure where it's so much for the first n units, some lesser amount
> for units n+1 through m, and an even smaller amount for units m+1 and
> more.  Consequently, what I'd like to do is, after the array of
> purchase objects has be set up, redefine the amount() method for only
> the 5th purchase object to incorporate a formula that takes into
> account the graduated pricing structure.  IOW, I'd like to override
> the standard amount method definition for only the 5th object with a
> new definition.  My question is:  How would I do that?

Commercial systems typically solve this problem with the addition of a 
discount policy attribute. Your "amount" function would examine this 
attribute to determine which policy (of potentially many) applies to 
this transaction.

-- 

Best regards,

Morgan Simpson
Bray, Simpson & Associates, Inc.

+1 714 435 0150 - office
+1 714 390 5040 - cell
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