Jquery-多步骤表单进度条，使用无序列表项来显示已完成的步骤

我正试图用JQuery构建一个多步骤表单，但我的进度条出现了一些问题。

我的进度栏是一个无序的列表，其中的列表项应该在用户按下next时高亮显示为红色。但是，当他们按下上一个时，列表项目应该会失去突出显示的红色。我非常接近解决方案。我有前两个选项，但当我进入最后一步时，我没有看到任何突出显示。

这是我的小提琴：http://jsfiddle.net/ktLcfzhe/

JQuery：$（document）.ready（function（）｛

    var current_fs = $('.current'); //current fieldset   
    $('.next').click(function () {
        $('.current').removeClass('current').hide().next().show().addClass('current');

        if ($(this).parent('.field1')) {
            $('#progressbar li').next('.second').addClass('active');
        } else if ($(this).parent('.field2')) {
            $('#progressbar li').next('.last').addClass('active');
        } else if ($(this).parent('.field3')) {
            $('#progressbar li').addClass('active');
        }
    });
    $('.previous').click(function () {
        $('.current').removeClass('current').hide().prev().show().addClass('current');
        if ($(this).parent('.field3')) {
            $('#progressbar li').prev('.last').removeClass('active');
        } else if ($(this).parent('.field2')) {
            $('#progressbar li').prev('.second').removeClass('active');
        }

    });
});

HTML:

<form id="helpdeskform" action="process.php" method="post">
    <!-- Progress Bar -->
    <ul id="progressbar">
        <li class="active first">Identify Yourself</li>
        <li class="second">Describe Request</li>
        <li class="last">Confirm and Submit</li>
    </ul>
    <fieldset class="field1 current">
            <h2>Identify Yourself</h2>
        <p>
            <label for="fname">
                <input type="text" value="" name="" id="" placeholder="First Name" />
            </label>
        </p>
        <p>
            <label for="lname">
                <input type="text" value="" name="" id="" placeholder="Last Name" />
            </label>
        </p>
        <p>
            <label for="Next">
                <input type="button" name="next" class="next action-button" value="Next" />
            </label>
        </p>
    </fieldset>
    <fieldset class="field2">
            <h2>Describe Request</h2>
        <p>
            <label for="">
                <input type="text" value="" name="" id="" placeholder="Subject" />
            </label>
        </p>
        <p>
            <label for="">
                <textarea style="font-family: Arial, Veranda, Sans serif" name="" id="" cols="30" rows="10"></textarea>
            </label>
        </p>
        <p style="float:left;">
            <label for="previous">
                <input type="button" name="previous" class="previous action-button" value="Previous" />
            </label>
        </p>
        <p style="float:left; padding-left: 10px;">
            <label for="Next">
                <input type="button" name="next" class="next action-button" value="Next" />
            </label>
        </p>
    </fieldset>
    <fieldset class="field3">
            <h2>Confirm and Submit</h2>
        <p>
            <label for="fname">
                <input type="text" value="" name="" id="" placeholder="" />
            </label>
        </p>
        <p>
            <label for="">
                <input type="text" value="" name="" id="" placeholder="" />
            </label>
        </p>
        <p>
            <label for="">
                <input type="text" value="" name="" id="" placeholder="" />
            </label>
        </p>
        <p>
            <label for="">
                <input type="text" value="" name="" id="" placeholder="" />
            </label>
        </p>
        <p style="float:left;">
            <label for="previous">
                <input type="button" name="previous" class="previous action-button" value="Previous" />
            </label>
        </p>
        <p style="float:left; padding-left: 10px;">
            <label for="Submit">
                <input type="button" value="Submit" name="submit" id="submit" />
            </label>
        </p>
    </fieldset>
</form>

CSS：

/*form styles*/
 #helpdeskform {
    text-align: center;
    position: relative;
}
/*Hide all except first fieldset*/
 #helpdeskform .field2, .field3 {
    display: none;
}
/*inputs*/
 #helpdeskform input, #helpdeskform textarea {
    padding: 15px;
    border: 1px solid #ccc;
    border-radius: 3px;
    margin-bottom: 10px;
    width: 100%;
    box-sizing: border-box;
    color: #2C3E50;
    font-size: 13px;
}
/*buttons*/
 #helpdeskform .action-button {
    width: 100px;
    font-weight: bold;
    border: 0 none;
    border-radius: 1px;
    cursor: pointer;
    padding: 10px 5px;
    margin: 10px 5px;
}
#helpdeskform .action-button:hover, #msform .action-button:focus {
    box-shadow: 0 0 0 2px white, 0 0 0 3px #900;
}
/*progressbar*/
 #progressbar {
    margin-bottom: 30px;
    overflow: hidden;
    counter-reset: step;
    /*CSS counters to number the steps*/
}
#progressbar li {
    list-style-type: none;
    text-transform: uppercase;
    font-size: 10px;
    width: 30%;
    float: left;
    position: relative;
}
#progressbar li:before {
    content: counter(step);
    counter-increment: step;
    width: 20px;
    line-height: 20px;
    display: block;
    font-size: 10px;
    color: #333;
    background: white;
    border-radius: 3px;
    margin: 0 auto 5px auto;
}
/*progressbar connectors*/
 #progressbar li:after {
    content:'';
    width: 100%;
    height: 2px;
    background: white;
    position: absolute;
    left: -50%;
    top: 9px;
    z-index: -1;
    /*put it behind the numbers*/
}
#progressbar li:first-child:after {
    content: none;
    /*connector not needed before the first step*/
}
/*marking active/completed steps nhlbi red*/
/*The number of the step and the connector before it = red*/
 #progressbar li.active:before, #progressbar li.active:after {
    background: #900;
    color: white;
}

感谢所有意见。我曾经http://thecodeplayer.com/walkthrough/jquery-multi-step-form-with-progress-bar作为这个表单的指南。JQuery对我来说太复杂了。