This question already has an answer here:
<!DOCTYPE html>
<html>
<body bgcolor = "eeeeee">
<p> Add Section </p>
<label>Fir No :</label>
<input id="txt1" type="text"/></br></br>
<label>Sec No :</label>
<input id="txt2" type="text"/></br></br>
<input type="button" name="Add" value="Add" onclick="addTwoNumber()"/>
<p id="demo"></p>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = Date();
}
<!-- addition of two numbers-->
function addTwoNumber(){
var a = document.getElementById("txt1").value;
var b = document.getElementById("txt2").value;
var x = Number(a) + Number(b);
document.getElementById("demo").innerHTML = "Add Value: " + x;
}
</script>
</body>
</html>
i have written a code in this code i am not able to alert user if he enters other than number and also how to alert the user if he left blank without filling value in addition
