Question
How to check/validate a textbox has numeric value or not in asp.net using javascript ?
Also validate when textbox is null.
Answer
Suppose, we have a textbox on the form and it's ID='txtAge'. and we also have a button control
and it's ID='btn1' Now this is the javascript code :
<script
type="text/javascript">
function validate() {
var age = document.getElementById('<%=txtAge.ClientID
%>').value;
if age== "") {
alert('enter
age');
return false;
}
else {
if (isNaN(age)) {
alert('enter
a valid age');
return false;
}
}
}
</script>
Now you have to set the Button(btn1) onclientclick property.
For example
onclientclick="return validate();"
Conclusion
Using this we can check that a textbox has value or not. If it is not then it
shows alert to enter text. And, if the textbox has value then we check that the
entered value is numeric or not.