Prevent Characters

by joshkrz

HTML

<input type="text"/>

JavaScript

$(document).ready(function () {
    
    $('input').keyup(function() {
        var $th = $(this);
        $th.val( $th.val().replace(/[^a-zA-Z0-9]/g, function(str) { alert('You typed " ' + str + ' ".\n\nPlease use only letters and numbers.'); return ''; } ) );
    });
});