jQuery(document).ready(function ($) {

    var selectors = [
        'input[type=text]',
        'input[type=email]',
        'input[type=url]',
        'input[type=tel]',
        'input[type=number]',
        'input[type=date]',
        'input[type=file]',
        'textarea',
        'select'
    ];

    var onFilled = function (ev) {
        var el = $(ev.target);
        if (el.val() && !el.hasClass('filled')) {
            el.addClass('filled');
        } else {
            el.removeClass('filled');
        }
    };

    var form = $('.wpcf7-form');

    $(selectors.join(), form)
        .on('focus', $.proxy(onFilled, this))
        .on('blur', $.proxy(onFilled, this));

});