markdown-it代码块渲染、自定义行号、复制代码功能

之前写过一篇关于代码块渲染添加自定义行号的文章：markdown-it和highlight.js的结合渲染代码，并添加自定义行号 。

不过在之后的渲染使用过程中由于效果不是很好，所以重新改版，并借此机会添加复制代码功能。

本博客采用的后端是 node.js 框架 Express，在使用 markdown-it 渲染 md 文件的时候，选择在添加文章或者更新文章的时候由 md 生成 html。

代码块生成

const md = new MarkdownIt({
  html: true,
  linkify: true,
  typographer: true,
  highlight: function (str, lang) {
    // 当前时间加随机数生成唯一的id标识
    const codeIndex = parseInt(Date.now()) + Math.floor(Math.random() * 10000000)
    // 复制功能主要使用的是 clipboard.js
    let html = `${codeIndex}">复制`
    const linesLength = str.split(/\n/).length - 1
    // 生成行号
    let linesNum = ''
    for (let index = 0; index < linesLength; index++) {
      linesNum = linesNum + ''
    }
    linesNum += ''
    if (lang && hljs.getLanguage(lang)) {
      try {
        // highlight.js 高亮代码
        const preCode = hljs.highlight(lang, str, true).value
        html = html + preCode
        if (linesLength) {
          html += '' + lang + ''
        }
        // 将代码包裹在 textarea 中
        return `
${html}${linesNum}
<span class="token interpolation-punctuation punctuation">${</span>codeIndex<span class="token interpolation-punctuation punctuation">}</span></span><span class="token string">"></span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">${</span>str<span class="token punctuation">.</span><span class="token function">replace</span><span class="token punctuation">(</span><span class="token regex">/<\/textarea>/g</span><span class="token punctuation">,</span> <span class="token string">'</textarea>'</span><span class="token punctuation">)</span><span class="token interpolation-punctuation punctuation">}</span></span><span class="token string">`
      } catch (error) {
        console.log(error)
      }
    }

    const preCode = md.utils.escapeHtml(str)
    html = html + preCode
    // 将代码包裹在 textarea 中
    return `
${html}${linesNum}
<span class="token interpolation-punctuation punctuation">${</span>codeIndex<span class="token interpolation-punctuation punctuation">}</span></span><span class="token string">"></span><span class="token interpolation"><span class="token interpolation-punctuation punctuation">${</span>str<span class="token punctuation">.</span><span class="token function">replace</span><span class="token punctuation">(</span><span class="token regex">/<\/textarea>/g</span><span class="token punctuation">,</span> <span class="token string">'</textarea>'</span><span class="token punctuation">)</span><span class="token interpolation-punctuation punctuation">}</span></span><span class="token string">`
  }
})

前端

前端实现代码选中的功能：

import Clipboard from 'clipboard'

export default {
  ...
  data () {
    return {
      ...
      clipboard: ''
    }
  },
  mounted () {
    this.$nextTick(() => {
      this.clipboard = new Clipboard('.copy-btn')
      // 复制成功失败的提示
      this.clipboard.on('success', (e) => {
        this.$message.success('复制成功')
      })
      this.clipboard.on('error', (e) => {
        this.$message.error('复制成功失败')
      })
    })
  },
  ...
  destroyed () {
    this.clipboard.destroy()
  }
}

自定义行号

pre.hljs {
  padding: 12px 2px 12px 40px !important;
  border-radius: 5px !important;
  position: relative;
  font-size: 14px !important;
  line-height: 22px !important;
  overflow: hidden !important;
  code {
    display: block !important;
    margin: 0 10px !important;
    overflow-x: auto !important;
  }
  .line-numbers-rows {
    position: absolute;
    pointer-events: none;
    top: 12px;
    bottom: 12px;
    left: 0;
    font-size: 100%;
    width: 40px;
    text-align: center;
    letter-spacing: -1px;
    border-right: 1px solid rgba(0, 0, 0, .66);
    user-select: none;
    counter-reset: linenumber;
    span {
      pointer-events: none;
      display: block;
      counter-increment: linenumber;
      &:before {
        content: counter(linenumber);
        color: #999;
        display: block;
        text-align: center;
      }
    }
  }
  b.name {
    position: absolute;
    top: 2px;
    right: 50px;
    z-index: 10;
    color: #999;
    pointer-events: none;
  }
  .copy-btn {
    position: absolute;
    top: 2px;
    right: 4px;
    z-index: 10;
    color: #333;
    cursor: pointer;
    background-color: #fff;
    border: 0;
    border-radius: 2px;
  }
}

自定义行号主要使用的是CSS计数方面的知识，感兴趣可以查看 css计数器 。