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Why are my JavaScript variables not persisting across functions?

Answer 1

+7 A:

Your problem is in document.myForm. You may want to use:

var myForm = document.getElementById('myForm');

UPDATES: The other answers caught another couple of issues:

As bobobobo noted in another answer, you should use document.getElementById() for myForm.myInput as well. In addition outis caught another problem as you should place your <script> block near the end of your HTML document, just before the closing </body> tag. Otherwise your script will execute before the form gets inserted in the DOM.

Daniel Vassallo 2010-05-03 13:10:35

You beat me to it +1

Romain Hippeau 2010-05-03 13:13:25

Answer 2

+10 A:

What browser are you using?

IN general you should never use document.* access. This is an MS-IE convention. Instead, use

var myForm = document.getElementById( 'myForm' ) ;
var myInput = document.getElementById( 'myInput' ) ;

if( myInput.value == '' )
{
    // its empty!
}

As outis noted, either put your script block at the bottom of your page, or use the onload event of <body> tag, like this

<script>
function go()
{
    alert( "The DOM has been assembled and can be accessed.. nOW!!!" ) ;
    var myForm = document.getElementById( 'myForm' ) ; // ...
}
</script>
<body onload="go() ;">
</body>

bobobobo 2010-05-03 13:15:10

+1 for catching the other problem :)

Daniel Vassallo 2010-05-03 13:17:49

Thanks. I'm going to avoid document.* from now on.

Eric Belair 2010-05-04 14:27:11

Answer 3

+7 A:

If the sample is representative of the page, the the form "myForm" doesn't exist when the script is evaluated. In addition to using document.getElementById (or document.forms.formName), you'll need to delay setting var myForm until after the form element is processed or, better yet, pass the form as an argument to the functions rather than using a global variable.

outis 2010-05-03 14:06:05

+1 good catch ...

Daniel Vassallo 2010-05-03 14:29:16

I thought this might be the problem. It makes sense. Thank you.

Eric Belair 2010-05-03 17:00:07

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Why are my JavaScript variables not persisting across functions?

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