javascript validaion problem

i am new in programming i want to do validation but
other code in my ff.js file like code for checking the empty field is working
but the below one for checking numeric fields not working
ph_r2 is text field where i want to enter the numeric only since it is for phone no
if (!isNum(document.frmemp.ph_r2.value))
{
alert("Pl Enter Numeric Values")
document.frmemp.ph_r2.focus();
return false;
}

p. help

well, this code can make sure only numbers are entered during the keypress event of a form field..

Code:

---

function NumbersOnly(e) {
        var myChar;
        var badChar = "!@#$%^&*()-=+[]{}\\|;:'\",./<>_`~?ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz "
        //this only allows numbers
       
        e = window.event;
        myChar = String.fromCharCode(e.keyCode);
 
        for(var j = 0; j <= badChar.length-1; j++){
                if ( myChar == badChar.charAt(j) )
                        e.returnValue = false
        }
}

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