一、CSS部分：
.tree {
min-height:20px;
padding:19px;
margin-bottom:20px;
background-color:#fbfbfb;
border:1px solid #999;
-webkit-border-radius:4px;
-moz-border-radius:4px;
border-radius:4px;
-webkit-box-shadow:inset 0 1px 1px rgba(0, 0, 0, 0.05);
-moz-box-shadow:inset 0 1px 1px rgba(0, 0, 0, 0.05);
box-shadow:inset 0 1px 1px rgba(0, 0, 0, 0.05)
}
.tree li {
list-style-type:none;
margin:0;
padding:10px 5px 0 5px;
position:relative
}
.tree li::before, .tree li::after {
content:'';
left:-20px;
position:absolute;
right:auto
}
.tree li::before {
border-left:1px solid #999;
bottom:50px;
height:100%;
top:0;
width:1px
}
.tree li::after {
border-top:1px solid #999;
height:20px;
top:25px;
width:25px
}
.tree li span {
-moz-border-radius:5px;
-webkit-border-radius:5px;
border:1px solid #999;
border-radius:5px;
display:inline-block;
padding:3px 8px;
text-decoration:none
}
.tree li.parent_li>span {
cursor:pointer
}
.tree>ul>li::before, .tree>ul>li::after {
border:0
}
.tree li:last-child::before {
height:30px
}
.tree li.parent_li>span:hover, .tree li.parent_li>span:hover+ul li span {
background:#eee;
border:1px solid #94a0b4;
color:#000
}
.icon-plus-sign{display:inline-block;width:16px;height:16px;background:url('../Images/bg/ico_small.png') left -44px no-repeat;}
.icon-minus-sign{display:inline-block;width:16px;height:16px;background:url('../Images/bg/ico_small.png') left 0px no-repeat;}
完全可以自己建一个Css文件，将他们考入，引用。
.tree li::before, .tree li::after {}
.tree li::before {}
.tree li::after {}主要用上面三个属性实现树的前面树形线，注意是用css3的before 和after实现
二、HTML部分：
<div class="tree well">
<ul>
<li>
<span><i class="icon-plus-sign"></i> Parent</span><a href="">Goes somewhere</a>
<ul>
<li>
<span><i class="icon-plus-sign"></i> Child</span> <a href="">Goes somewhere</a>
<ul>
<li>
<span><i class="icon-leaf"></i> Grand Child</span> <a href="">Goes somewhere</a>
</li>
</ul>
</li>
<li>
<span><i class="icon-plus-sign"></i> Child</span> <a href="">Goes somewhere</a>
<ul>
<li>
<span><i class="icon-leaf"></i> Grand Child</span> <a href="">Goes somewhere</a>
</li>
<li>
<span><i class="icon-plus-sign"></i> Grand Child</span> <a href="">Goes somewhere</a>
<ul>
<li>
<span><i class="icon-plus-sign"></i> Great Grand Child</span> <a href="">Goes somewhere</a>
<ul>
<li>
<span><i class="icon-leaf"></i> Great great Grand Child</span> <a href="">Goes somewhere</a>
</li>
<li>
<span><i class="icon-leaf"></i> Great great Grand Child</span> <a href="">Goes somewhere</a>
</li>
</ul>
</li>
<li>
<span><i class="icon-leaf"></i> Great Grand Child</span> <a href="">Goes somewhere</a>
</li>
<li>
<span><i class="icon-leaf"></i> Great Grand Child</span> <a href="">Goes somewhere</a>
</li>
</ul>
</li>
<li>
<span><i class="icon-leaf"></i> Grand Child</span> <a href="">Goes somewhere</a>
</li>
</ul>
</li>
</ul>
</li>
<li>
<span><i class="icon-plus-sign"></i> Parent2</span> <a href="">Goes somewhere</a>
<ul>
<li>
<span><i class="icon-leaf"></i> Child</span> <a href="">Goes somewhere</a>
</li>
</ul>
</li>
</ul>
</div>三、JQ:
<script type="text/javascript">
var d=true;
$(function () {
$('.tree li:has(ul)').addClass('parent_li').find(' > span').attr('title', 'Collapse this branch');
$('.tree li.parent_li > span').on('click', function (e) {
var d = $(this).siblings('ul').is(":visible");
$(this).siblings('ul').slideToggle('fast');//.siblings('dt').css('background-position','right -40px');
if (d) {
console.log($(this).find(">i"));
$(this).find(">i").addClass('icon-minus-sign').removeClass('icon-plus-sign');
} else {
// $(this).find(' > i').addClass('icon-minus-sign').removeClass('icon-plus-sign');
$(this).find(">i").addClass('icon-plus-sign').removeClass('icon-minus-sign');
}
e.stopPropagation();
});
});
</script>4、树形折叠图片：
为这两个样式准备
.icon-plus-sign{display:inline-block;width:16px;height:16px;background:url('../Images/bg/ico_small.png') left -44px no-repeat;}
.icon-minus-sign{display:inline-block;width:16px;height:16px;background:url('../Images/bg/ico_small.png') left 0px no-repeat;}
原文：https://blog.csdn.net/pt_sm/article/details/73287511
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