Hola:
Tal vez te interese crear ese array en el momento de necesitarlo:
Código:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>
http://www.caricatos.net/probador
</title>
<script type="text/javascript" >
var chs = new Array();
function mostrarChecks() {
chs = new Array();
f = document.forms[0];
for (i = 0, total = f.ch.length; i < total; i ++)
if (f.ch[i].checked) chs.push(f.ch[i].value);
}
</script>
</head>
<body>
<form onsubmit="mostrarChecks()" action="javascript: alert(chs)" >
<input type="checkbox" name="ch" value="ch1" />
<input type="checkbox" name="ch" value="ch2" />
<input type="checkbox" name="ch" value="ch5" />
<input type="checkbox" name="ch" value="ch6" />
<input type="checkbox" name="ch" value="ch7" />
<input type="checkbox" name="ch" value="ch8" />
<button type="submit" >ver</button>
</form>
</body>
</html>
Saludos