Question

I really don’t know what the issue is here. As far as I can see, the code is simple and should work fine.

          var Prices="";
          for (var PriceCount = 1; PriceCount <= 120; PriceCount++) {
              var CurrentPrice = "Price" + PriceCount;
              if (prevDoc.getElementById(CurrentPrice).value != null) {
                  if (Prices == "") {
                      Prices = prevDoc.getElementById(CurrentPrice).value;
                  } else {
                      Prices += "," + prevDoc.getElementById(CurrentPrice).value;
                  }
              } else {
                  break;
              }
          }

There could be up to 120 hidden inputs on the form. The moment we check for an input that doesn’t exist the loop should break. My test page has two input elements that get pulled. On the third (the null) I get this error in firebug:

prevDoc.getElementById(CurrentPrice) is null

 if (prevDoc.getElementById(CurrentPrice).value != null) {

Yes it is null…that’s what the check is for ಠ_ಠ

Does any one know what I’m doing wrong? This seems like it should be really straight forward.

EDIT:
for clarity’s sake, prevDoc=window.opener.document

Answer 1

if (prevDoc.getElementById(CurrentPrice).value != null) {

can be expanded to:

var element = prevDoc.getElementById(CurrentPrice);    
var value = element.value; /* element is null, but you're accessing .value */

if (value != null) {