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I'm trying to understand how to use firebug to debug my Javascript. So I have the HTML listed below. And I want to set a watch expression on the var 's'. I went to the Script tab of Firebug and opened the Watch pane and entered s into the area that says "New watch expression".
I get an error:
ReferenceError: s is not defined
Why?
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">
.StateOne .InitiallyHidden { display: none; }
.StateTwo .InitiallyVisible { display: none; }
</style>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
<script language="javascript" type="text/javascript">
$(document).ready(function()
{
$('.x').click(function() {
var s = $("#StateContainer")[0];
s.className = (s.className == 'StateOne' ? 'StateTwo' : 'StateOne');
});
});
</script>
</head>
<body>
<button class="x">Change StateContainer</button>
<div class="StateOne" id="StateContainer">
<div class="InitiallyVisible">Visible first</div>
<div class="InitiallyHidden">Visible second</div>
<div class="InitiallyVisible">Visible first</div>
<div class="InitiallyHidden">Visible second</div>
<div class="InitiallyVisible">Visible first</div>
<div class="InitiallyHidden">Visible second</div>
<div class="InitiallyVisible">Visible first</div>
<div class="InitiallyHidden">Visible second</div>
</div>
</body>
</html>
872
The variable 's' is only defined inside the click handler for 'x' because it is declared within the function. If you set a breakpoint inside your click function then 's' will work.
It's generally not good practice to create global variables, but for the sake of debugging you could make 's' a global variable by declaring it outside of the $(document).ready() function, like so:
<script language="javascript" type="text/javascript">
var s;
$(document).ready(function()
{
$('.x').click(function() {
s = $("#StateContainer")[0];
s.className = (s.className == 'StateOne' ? 'StateTwo' : 'StateOne');
});
});
</script>
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