Set the onfocusout event for this button as shown below.

  1. <div>Mobile No: <input type="number" id="phonenumber" onfocusout="mobilecheck();"></div>

Create a function representing a link to that button and it gets executed when triggered.

  1. function mobilecheck() {
  2. var mobile = document.getElementById("phonenumber").value;
  3. var pattern = /^[1-9]{1}[0-9]{9}$/;
  4. //var eml = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
  5. if (pattern.test(mobile)) {
  6. //alert("Your mobile number : " + mobile);
  7. return true;
  8. }
  9. alert("It is not a valid mobile number. Please input 10 digits only!");
  10. return false;
  11. }
Go to the site page and start filling in the details.
Here the validation message for Mobile number pops up, if entered wrong.
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