$(document).ready(function () {
    $('#btnAdd').click(function () {
        var num = $('.clonedInput').length; // how many "duplicatable" input fields we currently have
        var newNum = new Number(num + 1);      // the numeric ID of the new input field being added

        // create the new element via clone(), and manipulate it's ID using newNum value
        var newElem = $('#input' + num).clone().attr('id', 'input' + newNum);

        // manipulate the name/id values of the input inside the new element
        newElem.children(':first').attr('id', 'author' + newNum).attr('name', 'author' + newNum).attr('value', 'enter a name');

        // insert the new element after the last "duplicatable" input field
        $('#input' + num).after(newElem);

        // enable the "remove" button
        $('#btnDel').attr('disabled', '');

        // business rule: you can only add 5 names
        if (newNum == 5)
            $('#btnAdd').attr('disabled', 'disabled');
    });

    $('#btnDel').click(function () {
        var num = $('.clonedInput').length; // how many "duplicatable" input fields we currently have
        $('#input' + num).remove();     // remove the last element

        // enable the "add" button
        $('#btnAdd').attr('disabled', '');

        // if only one element remains, disable the "remove" button
        if (num - 1 == 1)
            $('#btnDel').attr('disabled', 'disabled');
    });

    $('#btnDel').attr('disabled', 'disabled');
});