To create a widget that takes a user’s input of Postcode, compares it against an array of postcodes, and acts on the page telling the user whether their postcode is valid or not, you can start with the following code: <div id="MyForm"> <form method="POST" name="info-form"> <input type="hidden" value="/form-sent" name="returnURL" /> <label for="First Name">First Name: </label>…