仅通过 css 为代码添加行号 | code line number with CSS only
效果图：
完整代码：
<style>
pre > code{display:block;color:#fff;background:#282c34;/*font-size: 18px;line-height: 22px;border-radius:20px;width:80%;margin:0 auto;height:100%;overflow-y: scroll;*/padding:10px 20px;word-wrap: break-word;white-space: pre-wrap;
}/* code line number
https://webtips.dev/add-line-numbers-to-html-textarea
*/
pre{counter-reset: linenumber;}
pre > code > span::before{content: counter(linenumber, decimal-leading-zero) " ";counter-increment: linenumber;color:#506882;
}
/*
pre > code > span{display: block;}
*/
</style><pre><code>$ cat ./code/w.step2.FigureS22.MAIT_Tex.R
<br>
<span># This is a very long line. This is a very long line. This is a very long line. This is a very long line. This is a very long line. </span>
<span>library("Seurat")</span>
<span></span>
<span>RhpcBLASctl::omp_set_num_threads(1)</span>
<span>doParallel::registerDoParallel(cores=8)</span>
<span>options(stringsAsFactors=F)</span>
<span></span>
<span>oDir = "./OUT_FigS22"</span>
<span>dir.create(oDir, F, T)</span></code>
</pre>