SOURCE

<!-- CSS 也能自动补全字符串？ -->
<!-- https://mp.weixin.qq.com/s/tzcE15njxxHD4ihkwtoDTg -->
<!-- 
counter-reset: 创建一个计数器;
counter-increment: 增加或减少计数器的值;
counter(): 展示计数器的值. 通常搭配在伪类元素中搭配 content 属性使用.
 -->
<style>
    .box{
       
    }
    span::before{
        counter-reset:num var(--num);
        /* counter-increment: num; */
         /* content: counter(num); */
        /* content: counter(num, decimal-leading-zero); */
        content: counter(num, pad-num);
    }

     @counter-style pad-num {
        system: extends numeric;
        pad: 3 "0";
    }
</style>

<div class="box">
<span style="--num:1">aaaaa</span>
<span style="--num:99">bbbbb</span>
<span style="--num:99">cccc</span>


</div>