Redirect Website for Mobile Devises

If I use the following script, do I have to put it on every page and update the document.location = "mobile.html" for every page?

<script type="text/javascript">
<!--
if (screen.width <= 699) {
document.location = "mobile.html";
}
//-->
</script>

##################################################

Example would be:

Page 1

<script type="text/javascript">
<!--
if (screen.width <= 699) {
document.location = "mobile_page1.html";
}
//-->
</script>

Page 2

<script type="text/javascript">
<!--
if (screen.width <= 699) {
document.location = "mobile_page2.html";
}
//-->
</script>

Is there an easier way to redirect with .htaccess?