markdown-tree.js

const fs = require('fs'),
      path = require('path')
function spaceAhead(n) {
  let outputString = ''
  for (let i = 0; i < n; i++) {
    outputString += ' '
  }
  return outputString
}

function analyze(rootDir, dirname, identation=0) {
  let outputString = ''
  const files = fs.readdirSync(dirname)
  let foundMarkdownFile = false
  files.forEach((fileName)=> {
    if (fileName.endsWith('.md')) { // is markdown file
      foundMarkdownFile = true
      outputString += spaceAhead(identation + 4) + '* [' + path.basename(fileName).replace(path.extname(fileName), '')  + ']('+path.relative(rootDir, path.resolve(dirname, fileName)) + ')\n'
    } else if (fs.lstatSync(path.resolve(dirname, fileName)).isDirectory()) { // is directory
      const {out, found} = analyze(rootDir, path.resolve(dirname, fileName), identation + 4)
      foundMarkdownFile = foundMarkdownFile || found
      outputString += out
    }
  })

  if (foundMarkdownFile) {
    outputString = spaceAhead(identation) + '* ' + path.basename(dirname) + '\n' + outputString
  }

  return {
    out: outputString,
    found: foundMarkdownFile
  }
}

const files = fs.readdirSync(__dirname)
const outputString = files.map((fileName)=> {
  if (fs.lstatSync(path.resolve(__dirname, fileName)).isDirectory()) {
    return analyze(__dirname, path.resolve(__dirname, fileName), 0).out
  } else {
    return ''
  }
}).join('')

console.log(outputString)