Why this not working

[eric_2005]

Hi,

I got multiple rows with same COMBOX BOX ,differentiated with its row ID.

I am able to get the row id no. But, with rowid when i
try to get the selection box element length, it fails .

By doing directly like this, i am getting value.
----> alert(document.forms[0].rowid_1.options.length);

But with this one gives error,

========================================

var x = 1;
var rowid = 1;
var comboid="document.forms[0].row_" +rowid;
alert(comboid.options.length);
====================

Error : 'options.length' is null or not an object.
========================================


Please help me to solve this ...(:

[mwinter]

var rowid = 1;
var comboid="document.forms[0].row_" +rowid;

At this point, the value of comboid will be:

  document.forms[0].row_1

However, it is a string value.

alert(comboid.options.length);

When the property access occurs with this function call, the string value will be temporarily converted to a String object, and the interpreter will attempt to find an options property. Strings do not have such a property (by default), so that part of the expression will evaluate to undefined. Trying to get a property from an undefined value results in an error.

What you should do is use bracket notation to construct the property name:

document.forms[0].elements['row_' + rowid].options.length

The string concatenation you can see above will create the string value, 'row_1', the name of the property you want.

The above is equivalent to:

document.forms[0].elements.row_1.options.length

but achieved dynamically.

Mike

[eric_2005]

I tried, with your code, but same error . Any other suggestions,please (:

[Twey]

This should have fixed it. Can you post the code you're using now, with Mike's modifications in?