Object help needed

[MikeS]

I'm trying to add items to a shopping cart, if the item is already added I
want to just increase the quantity by 1 instead for adding a new Item, I've
got it nearly working for the first item ...but after that it just keeps
adding a new Item. What am I doing wrong - I've been racking my brains
trying to figure this out all day.

function additem(desc,pr ice,quantity) {
if (numitems>=1){
for(i=1;i<=numi tems;i++) {
if(cart[i].desc == desc){
++cart[i].quantity
}
else{
cart[++numitems] = new Item(desc,price ,quantity);
}
displaycart();
}
}else{
cart[++numitems] = new Item(desc,price ,quantity);
displaycart();
}
}

Thanks
Mike

[Janwillem Borleffs]

Re: Object help needed


"MikeS" <nospam@secure. f9.co.uk> schreef in bericht
news:behmdh$5c3 dc$1@ID-27598.news.dfnc is.de...[color=blue]
> I'm trying to add items to a shopping cart, if the item is already added I
> want to just increase the quantity by 1 instead for adding a new Item,[/color]
I've[color=blue]
> got it nearly working for the first item ...but after that it just keeps
> adding a new Item. What am I doing wrong - I've been racking my brains
> trying to figure this out all day.
>
> function additem(desc,pr ice,quantity) {
> if (numitems>=1){
> for(i=1;i<=numi tems;i++) {
> if(cart[i].desc == desc){
> ++cart[i].quantity
> }
> else{
> cart[++numitems] = new Item(desc,price ,quantity);
> }
> displaycart();
> }
> }else{
> cart[++numitems] = new Item(desc,price ,quantity);
> displaycart();
> }
> }
>[/color]

When the second condition equals true, the value of numitems will be
increased, which causes an infinite loop.

Instead of using [++numitems], do it like [numitems+1]. This doesn't affect
the value of numitems.


JW

[Daniel]

Re: Object help needed


"Janwillem Borleffs" <jwb@jwbfoto.de mon.nl> wrote in message
news:3f0c870f$0 $28903$1b62eedf @news.euronet.n l...[color=blue]
> When the second condition equals true, the value of numitems will be
> increased, which causes an infinite loop.
>
> Instead of using [++numitems], do it like [numitems+1]. This doesn't[/color]
affect[color=blue]
> the value of numitems.[/color]

Just adding to this:

The ++ operand always increases a variable's value by 1, but works in two
ways depending on where you put it -

var i = 0;
var j = 0;

alert(i++); // Outputs 0
alert(i); // Outputs 1

alert(++j); // Outputs 1
alert(j); // Outputs 1

- in other words, putting ++ *before* the variable increases its value
*before* it's evaluated, putting ++ *after* increases the value *after*. So,
these for loops do exactly the same:

for(var i=0;i<myArray.l ength; i++){
alert(myArray[i]);
}

for(var i=0;i<myArray.l ength;){
alert(myArray[i++]);
}

for(var i=-1;i<myArray.len gth-1;){
alert(myArray[++i]);
}

Just in case you didn't know =)


Cheers,
Daniel



--
There are 10 kinds of people: Those who know binary and those who don't.

[MikeS]

Re: Object help needed

"MikeS" <nospam@secure. f9.co.uk> wrote in message
news:behmdh$5c3 dc$1@ID-27598.news.dfnc is.de...

I'm nearly there...

Ok, after looping through the array and only if the item is not found I want
to add this as a new Item What am I missing from the code below?

function additem(desc,pr ice,quantity) {

for(i=1;i<=numi tems;i++) {
if(items[i].desc == desc){
++items[i].quantity;
}
}

items[++numitems] = new Item(desc,price ,quantity);

displaycart();
}