<ul>
<li><span title="内容11111">内容11111</span></li>
<li><span title="内容222222222222">内容222222222222</span></li>
<li><span title="内容3dddd33">内容3dddd33</span></li>
</ul>
li{
display: inline-block;
}
li span{
font-size: 14px;
}
span:hover{
font-weight: 700;
}
span::before{
content: attr(title);
font-weight: 700;
display: block;
height: 0;
visibility: hidden;
overflow: hidden;
}