숫자만 입력되었는지 체크

<form name="checknum" onSubmit="return checkban()">
숫자만 입력받는 항목 : <br>
<input type="text" name="pnum">
<input type="submit" value="Submit">
</form>

<script language="JavaScript1.2">
function checknumber(){
    var x=document.checknum.pnum.value
    var anum=/(^\d+$)|(^\d+\.\d+$)/
    if (anum.test(x))
        testresult=true
    else{
        alert("숫자만 입력가능합니다.!")
        testresult=false
    }
return (testresult)
}

function checkban(){
    if (document.layers||document.all||document.getElementById)
    return checknumber()
    else
    return true
}
</script>