Weid behaviour calling value of a selfmade JS class

**frenkieb** · Mar 12, 2007 03:31

Hi,

I experienced some weird behaviour when alerting the value of a selfmade JS class.

I made the class myTestobj with one property called 'value'. The object 'mytest' is of that type. If I alert 'mytest.value' before the formtag it says 'Normal behaviour' as expected. But when I alert it inside the form it says 'Not so normal behaviour!'.

As you can see I have an element with the name 'mytest' in the form.
Why does it alert the value of this element when I call it inside the form and not the value of my object?

HTML Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="nl" lang="nl">
<head>
  <title>Weird behaviour</title>	
  <script type="text/javascript">
    function myTestobj(){
      this.value = 'Normal behaviour';
    }
				
    var mytest = new myTestobj();
  </script>
 </head>
  
  <body>
    <input type="button" onclick="alert(mytest.value);" value="Before the form">
    <form>
      <input type="button" onclick="alert(mytest.value);" value="In the form">
        <table>
	  <tr>
	    <td><input type="text" name="mytest" value="Not so normal behaviour!" /></td>
	  </tr>
	</table>
    </form>
  </body>
</html>

**7stud** · Mar 12, 2007 03:42

Go through your js and your html and write down every variable name you use and every name you assigned to a name attribute. Create columns for each name, and put tick marks under the column headings every time you use a name. Also add an extra tick mark under "value" since js uses that name as well.

**Kravvitz** · Mar 12, 2007 09:13

It does that because inside the form the the form control named "mytest" gets reached before the global variable named "mytest" when the parser tries to resolve the reference.

To get around that, you can specify the object to which the variable is attached. Global variables get attached to window, so you can refer to it as window.mytest.value.

**frenkieb** · Mar 12, 2007 09:17

Ah thank you Kravvitz, that makes a lot of sense!

Not so weird behaviour after all.

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