javascript只能輸入數字

＜body>
＜script>
function JHshNumberText()
{
if ( !(((window.event.keyCode >= 48) && (window.event.keyCode ＜= 57)) (window.event.keyCode == 13) (window.event.keyCode == 46) (window.event.keyCode == 45)))
{window.event.keyCode = 0 ;}
}
＜/script>
＜form name="frm">
＜input type="text" name="test" value="" onkeypress="JHshNumberText()">
＜input type="button" name="submit" value="submit">
＜/form>
＜/body>