PRB: Value of a Checkbox Interpreted Differently (186422)

SYMPTOMS

The following VBScript code produces different results when viewed by Internet Explorer 3.02 and Internet Explorer 4.01 or later (the full text of the HTML and VBScript code will be detailed in the next section):

<SCRIPT LANGUAGE="VBScript">
<!--
   sub submit_onclick
   if document.Info.sound.checked = True then msgbox "The checkbox is
   checked!"
   end sub
   -->
</SCRIPT>

Internet Explorer 3.02 does not interpret the value of the checkbox correctly. As a result, it does not execute the action in the THEN section of the IF/THEN statement.

CAUSE

Following is a full HTML and VBScript example:

Sample Code

<HTML>
<HEAD>
<TITLE>Checkbox test </TITLE>
</HEAD>
<BODY>
<FORM NAME="Info">
<center>
My test checkbox
<input name="sound" type="checkbox">
<INPUT value="Test the checkbox value" TYPE="button" NAME="CheckIt"
ALIGN=left>
<SCRIPT LANGUAGE="VBScript">
<!--
sub CheckIt_onclick
if document.Info.sound.checked = true then msgbox "The checkbox is checked!"
end sub
-->
</SCRIPT>
</FORM>
</BODY>
</HTML>

The VBScript Language Reference defines "True" as the value -1. Internet Explorer 3.02 incorrectly interprets "True" as 1. For example:

if document.Info.sound.checked = -1 then msgbox "The checkbox is clicked!"

if document.Info.sound.checked = 1 then msgbox "The checkbox is clicked!"

The first line displays the message box correctly when you view it with Internet Explorer 4.01 or later, but not with Internet Explorer 3.02. Conversely, the second line displays the message box correctly when you use Internet Explorer 3.02, but not Internet Explorer 4.01 or later.

RESOLUTION

You can display the message box correctly in both versions of Internet Explorer by removing the explicit comparison to a value (True, 1 or -1) and allowing Internet Explorer to implicitly evaluate the statement. For example:

if document.Info.sound.checked then msgbox "The checkbox is checked!"

By doing this, it is implied that document.Info.sound.checked is evaluated to True or False. VBScript makes the comparison correctly.