javascript 支持ie和firefox杰奇翻页函数

<script type="text/javascript">
<!--
var preview_page = "{?$preview_page?}";
var next_page = "{?$next_page?}";
var index_page = "{?$index_page?}";
var article_id = "{?$article_id?}";
var chapter_id = "{?$chapter_id?}";

function jumpPage() {
var event=document.all?window.event:arguments[0];
  if (event.keyCode==37) location=preview_page;
  if (event.keyCode==39) location=next_page;
  if (event.keyCode==13) location=index_page;
}
document.onkeydown=jumpPage;
-->
</script>