input box restriction

by lemon kazi

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="firstname" type="text" />

JavaScript

$("#firstname, #lastname").on('input', function(event) {
  this.value = this.value.replace(/[^a-z\s]/gi, '');
});