[RESOLVED] Why did I have a use this temp var in this JS function?

dalecosp

I'm sure I've got membership on some JS forum or another, but can't be bothered to get a new password. I know some of us are pretty good with JS.

Why did I have to add the var "tmp" in the function below?

function check_duplicate_company_name() { // warn operator if name already entered
      var newCompanyName, companyListItems, i, tmp;

  newCompanyName = document.forms[0].elements[0].value;
  companyListItems = document.getElementsByClassName( 'company_name' );

  for ( i = 0; i <= companyListItems.length; ++i ) {

     tmp = companyListItems[i];
     if ( tmp.value == newCompanyName ) {
        alert( "Company Already Exists." );
        return false;
     }
  }
  submit_the_form();
   } //EOF

I tried "if (companyListItems.value == newCompanyName)" and got undefined errors. Why is that? Is there some concept I'm not understanding here?

Derokorian

Maybe because you're pre-incrementing (++i ) instead of post-incrementing (i++)? And then you would want to be just < length I believe... arrays are zero-indexed.

Compare the output:

var a = [1,2,3];
for (var i = 0; i<a.length; i++) { console.log(a[i]); }
// 1 2 3

for (var i = 0; i<=a.length; ++i) { console.log(a[i]); }
// 1 2 3 undefined

laserlight

Derokorian wrote:
Maybe because you're pre-incrementing (++i ) instead of post-incrementing (i++)?

In this context there is no difference: the expression is standalone. Rather the mistake has to do with the use of <= instead < as you also pointed out.

dalecosp

Thanks to both of you. I think I get it. So my "undefined" error was just one error at the end of the loop?

But I don't think I could get the alert to fire until I assigned companyListItems to tmp. In other words, this didn't seem to work:

function check_duplicate_company_name() { // warn operator if name already entered
      var newCompanyName, companyListItems, i;

  newCompanyName = document.forms[0].elements[0].value;
  companyListItems = document.getElementsByClassName( 'company_name' );

  for ( i = 0; i <= companyListItems.length; ++i ) {

     if ( companyListItems[i] == newCompanyName ) {
        alert( "Company Already Exists." );
        return false;
     }
  }
  submit_the_form();
   } //EOF

sneakyimp

I note that above your are comparing tmp.value to newCompanyName.

Perhaps this?

         if ( companyListItems[i].value == newCompanyName ) {
            alert( "Company Already Exists." );
            return false;
         }

dalecosp

sneakyimp;11050665 wrote:
I note that above your are comparing tmp.value to newCompanyName.

Perhaps this?
         if ( companyListItems[i].value == newCompanyName ) {
            alert( "Company Already Exists." );
            return false;
         }

Hmm, it might've indeed been that ... would've been easy to do. Alas, this code isn't in CVS, so I can't really tell ex-post-facto.