Learn to create a collapsible tree menu with pure CSS

With the release of CSS3, foreign research is in full swing, but there are still many people in China who hold the idea that IE does not support CSS3 and remain indifferent and refuse to learn. But history tells us that good things will prevail, and CSS3 will eventually replace CSS2. Let’s share with you a collapsible tree menu created with CSS3.

I believe everyone is familiar with the tree menu. We usually use css+JS to implement it. The arrival of CSS3 allows us to get rid of the constraints of JS and directly use the "selector" of CSS3 to realize a collapsible tree menu.

There is a lot of overall code, so I won’t go into it sentence by sentence. I will only mention what I think is important.

Html code:

<li>
<label for="subsubfolder1">下级</label>
<input id="subsubfolder1" type="checkbox" />
<ol>
<li class="file"><a>下级</a></li>
<li>
<label for="subsubfolder2">下级</label>
<input id="subsubfolder2" type="checkbox" />
<ol>
<li class="file"><a>无限级</a></li>
<li class="file"><a>无限级</a></li>
<li class="file"><a>无限级</a></li>
<li class="file"><a>无限级</a></li>
<li class="file"><a>无限级</a></li>
<li class="file"><a>无限级</a></li>
</ol>
</li>
</ol>
</li>

The idea of ​​implementation is to use the checked value of the checkbox to determine whether the lower-level column is expanded. The CSS3 selector provides the :checked pseudo-class. This pseudo-class provides us that when the element has checked Execute your CSS when the value is reached. (Very powerful, right? With CSS3, we will write a lot less JS!)

Downloader


When the checkbox has a checked value, let the OL appear to achieve the function we want.

Let’s take a look at the CSS code next:

li input {
position:absolute;left:0;margin-left:0;opacity:0;z-index:2;cursor:pointer;height:1em;width:1em;top:0;
}
input + ol {
display:none;
}
input + ol > li { 
height:0;overflow:hidden;margin-left:-14px!important;padding-left:1px; 
}
li label {
cursor:pointer;display:block;padding-left:17px;background:url(toggle-small-expand.png) no-repeat 0px 1px;
}
input:checked + ol {
background:url(toggle-small.png) 44px 5px no-repeat;margin:-22px 0 0 -44px;padding:27px 0 0 80px;height:auto;display:block;
}
input:checked + ol > li {
height:auto;
}

This code is the center of the tree menu:

input:checked + ol {
background: url(toggle-small.png) 44px 5px no-repeat; margin: -22px 0 0 -44px;padding:27px 0 0 80px;height: auto;display: block;
}

This is about the style owned by the OL of its level after inoput has checked.

You don’t need to read it if you are using IE9 or below. Please use a non-IE browser.

(It is also possible to make IE6+ browser support it, but you need to add JS to simulate css3 attributes. There are many talented people abroad who have written JS to let IE6+ browser support part of CSS3, such as PIE.)

Summary:

Overall Said, the implementation idea is very simple, mainly using the checked pseudo-class of CSS3 to realize the hidden display of OL. Unfortunately, the IE browser does not support CSS3, but we cannot give up research on CSS3 just because IE does not support it. CSS3 and HTML5 are both very hot topics in the front-end abroad. Their research far exceeds ours, but there are still not many people who have actually tried it in China, which is a very sad thing for a front-end developer. I think CSS3 should attract our attention and not let us lose at the starting line. Let us all work together to promote the development of CSS3.