Code
<html>
<head>
<script>
function init () {
var tables = document.getElementsByTagName("table");
for (var i = 0; i < tables.length; i++) {
if (tables[i].className.match(/zebra/)) {
zebra(tables[i]);
}
}
}
function zebra (table) {
var current = "oddRow";
var trs = table.getElementsByTagName("tr");
for (var i = 0; i < trs.length; i++) {
trs[i].className += " " + current;
current = current == "evenRow" ? "oddRow" : "evenRow";
}
}
</script>
<style>
tr.oddRow { background-color: green; }
tr.evenRow { background-color: red; }
</style>
</head>
<body onload="init()">
<table class="zebra">
<tr> <td>foo</td> <td>foo</td> <td>foo</td> </tr>
<tr> <td>bar</td> <td>bar</td> <td>bar</td> </tr>
<tr> <td>foo</td> <td>foo</td> <td>foo</td> </tr>
<tr> <td>bar</td> <td>bar</td> <td>bar</td> </tr>
<tr> <td>foo</td> <td>foo</td> <td>foo</td> </tr>
</table>
</body>
</html>