Question

I’m trying to generate form elements with jQuery to send to a Paypal form, I’m having issues looping through an array.

The list of items in a shopping cart is held in an array, the Javascript loops through the array adding the form fields and values as follows

for (j=0;j<(itemArray.length);j++)
$('#createFields').append("<input type='hidden' name='item_name_"+ j +"' value='"+itemArray[j]+"'/>");  

This works perfectly, except, I need item_name_ to begin with a 1, not a 0.

“easy” I thought

for (j=0;j<(itemArray.length);j++)
$('#createFields').append("<input type='hidden' name='item_name_"+ j+1 +"' value='"+itemArray[j]+"'/>");    

Should work, but no, that gives 01.

So I figured it wasn’t treating “j” as integer

So I tried

(j*1)+1

That still gave me 01

parseInt(j)+1

Also gives me 01!

How can I get “0+1 = 1” from this counter variable?!

I can’t understand why this issue is happening, I’ve got over the same problem with the methods above many times before!

I’ve also tried

for (j=1;j<( (itemArray.length+1) );j++)

but that just screws up the looping

Answer 1

Just group the expression:

"..." + (j+1) + "..."

this will give j + 1 a higher precedence so that it is evaluated first and then concatenated.

Otherwise, concatenation with the string will take place first, that is, first j is concatenated with the preceding string and then the resulting string is concatenated with 1 (left to right evaluation). Without grouping, the expression is implicitly evaluated as:

((("..." + j) + 1) + "...")