djonA,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script>
function test() {
for (var b = document.querySelectorAll("select.class"), a = 0; a < b.length; a++)
if ("0" == b[a].value) return false;
return true
};
</script>
</head>
<body>
<form onsubmit="return test();">
<select class="class">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
</select>
<select class="class">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
</select>
<input type="submit">
</form>
</body>
</html>