Scan recursively a directory to find all files, in the example we filter markdown(.md) files

RecursiveScan.js

const fs = require('fs');
const path = require('path');
/**
 * 
 * @param {String} Directory to scan
 * @param {Array} allFiles partial list of files(used for recursivity)
 */
const recursiveScan = function (directory, allFiles) {
  const files = fs.readdirSync(directory);
  allFiles = allFiles || [];

  files.forEach(function (file) {
    const stat = fs.statSync(path.join(directory, file));
    if (stat.isDirectory()) {
      /**
       * if it is a directory invoke the recursiveScan function passing the allFiles
       array to keep a reference of it
       */
      allFiles = recursiveScan(path.join(directory, file), allFiles);
    } else {
      allFiles.push(path.join(directory, file));
    }
  });
  return allFiles;
};

(async function () {
  /**
   * Markdown filter
   */
  const markDownFiles = recursiveScan('test').filter(file => file.indexOf(".md") >= 0);
  console.log(markDownFiles);
})();