Question

I have a simple form, which performs a calculation when a digit is pressed, however this should only happen when numbers are typed, if a letter is added i would like for a notification to appear. Is there a simple function to do this?

Form

    <input onKeyPress="return onlyNumbers()" onKeyUp="calc()" id="value1" type="text" name="value1">
    <select onChange="calc()" id="manipulator" name="manipulator">
        <option value="commission">Commission</option>
        <option value="cost">Return</option>
    </select>
</form>

calc function

function calc(){
    if (window.XMLHttpRequest){// code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
    } else {// code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }

    val1 = document.getElementById("value1").value;
    mani = document.getElementById("manipulator").value;

    if (val1 != ""){
        document.getElementById("resp").innerHTML="Calculating...";
        queryPath = "comCalcServ.php?value1="+val1+"&manipulator="+mani;

        xmlhttp.onreadystatechange=function(){
            if (xmlhttp.readyState==4 && xmlhttp.status==200){
                document.getElementById("resp").innerHTML=xmlhttp.responseText;
            }
        }

        xmlhttp.open("GET",queryPath);
        xmlhttp.send();
    }
}

I am currently looking at the isNaN function but not familiar with the JS syntax so unsure where to use it.

Answer 1

Do you mean:

//add inside your calc function
val1 = document.getElementById("value1").value;
if(/^\d+$/.test(val1)) {
 //proceed with rest of code
}
else {
 alert("Invalid");
 return false;
}