禁用表单向导中的“上一个”选项卡

Question

我的表单向导html包含预订表单的多个步骤如下：

<div class="container">
<div class="row">
<section>
<div class="wizard">
<div class="wizard-inner">
<div class="connecting-line"></div>
<ul class="nav nav-tabs" role="tablist">

<li role="presentation" class="active">
<a href="#step1" data-toggle="tab" aria-controls="step1" role="tab" title="Step 1">
<span class="round-tab">
<i class="fa fa-hospital-o" style="font-size:30px;"></i>
</span>
</a>
</li>

<li role="presentation" class="disabled">
<a href="#step2" data-toggle="tab" aria-controls="step2" role="tab" title="Step 2">
<span class="round-tab">
<i class="fa fa-heartbeat" style="font-size:30px;"></i>
</span>
</a>
</li>
<li role="presentation" class="disabled">
<a href="#step3" data-toggle="tab" aria-controls="step3" role="tab" title="Step 3">
<span class="round-tab">
<i class="fa fa-cc-visa" style="font-size:30px"></i>
</span>
</a>
</li>

<li role="presentation" class="disabled">
<a href="#complete" data-toggle="tab" aria-controls="complete" role="tab" title="Complete">
<span class="round-tab">
<i class="fa fa-check" style="font-size:30px"></i>
</span>
</a>
</li>
</ul>
</div>

<form role="form">
<div class="tab-content">
<div class="tab-pane active" role="tabpanel" id="step1">
<!--Start step 1-->
<p>

 <form>
  <div class="form-group">
    <label for="email">Email address:</label>
    <input type="email" class="form-control" id="email">
  </div>
  <div class="form-group">
    <label for="pwd">Password:</label>
    <input type="password" class="form-control" id="pwd">
  </div>
   <div class="form-group">
    <label for="email">Email address:</label>
    <input type="email" class="form-control" id="email">
  </div>
  <div class="form-group">
    <label for="pwd">Password:</label>
    <input type="password" class="form-control" id="pwd">
  </div>
</form> 
</p>
<!--End step 1-->

<ul class="list-inline pull-right">
<li><button type="button" class="btn btn-primary next-step">Save and continue</button></li>
</ul>
</div>
<div class="tab-pane" role="tabpanel" id="step2">
<h3>Step 2</h3>
<p>This is step 2</p>
<ul class="list-inline pull-right">
<li><button type="button" class="btn btn-primary next-step">Save and continue</button></li>
</ul>
</div>
<div class="tab-pane" role="tabpanel" id="step3">
<h3>Step 3</h3>
<p>This is step 3</p>
<ul class="list-inline pull-right">
<li><button type="button" class="btn btn-primary btn-info-full next-step">Save and continue</button></li>
</ul>
</div>
<div class="tab-pane" role="tabpanel" id="complete">
<h3>Complete</h3>
<p>You have successfully completed all steps.</p>
</div>
<div class="clearfix"></div>
</div>
</form>
</div>
</section>

javascript代码是：

$(document).ready(function () {
$('.nav-tabs > li a[title]').tooltip();
//Wizard
$('a[data-toggle="tab"]').on('show.bs.tab', function (e) {
var $target = $(e.target);
if ($target.parent().hasClass('disabled')) {
return false;
}
});
$(".next-step").click(function (e) {
var $active = $('.wizard .nav-tabs li.active');
$active.next().removeClass('disabled');
nextTab($active);
});
$(".prev-step").click(function (e) {
var $active = $('.wizard .nav-tabs li.active');
prevTab($active);
});
});
function nextTab(elem) {
$(elem).next().find('a[data-toggle="tab"]').click();
}
function prevTab(elem) {
$(elem).prev().find('a[data-toggle="tab"]').click();
}

我需要通过单击表单上方的选项卡图像，在前进的同时禁用前面的步骤。目前它已启用，我可以通过单击选项卡转到上一步。如何使用javascript代码禁用它？