functional.js

const fs = require('fs');

const DIRECTORY_COLOR = '\x1b[34m';
const FILE_COLOR = '\x1b[32m';

// -----------------------------------------------------------------------------
// Formatting
// -----------------------------------------------------------------------------

const buildPrefix = position => {
  const parentLine = new Array(5)
    .fill('│', 0, 1)
    .fill(' ', 1, 2)
    .join('');

  return new Array(position)
    .fill(parentLine, 0, position + 5)
    .concat('│─ ')
    .join('');
};

const getColor = isDirectory => (isDirectory ? DIRECTORY_COLOR : FILE_COLOR);

const printItem = (name, color, prefix) =>
  // eslint-disable-next-line
  console.log(`${color}${prefix}${name}`);

const printFile = (file, position = 0) => {
  printItem(file.filename, getColor(file.isDirectory), buildPrefix(position));
  file.files && file.files.forEach(item => printFile(item, position + 1));
};

// -----------------------------------------------------------------------------
// Helpers
// -----------------------------------------------------------------------------

const setBasePath = basePath => filename => `${basePath}/${filename}`;

const isDirectory = filename => fs.lstatSync(filename).isDirectory();

const isHidden = path => {
  const [filename] = path.split('/').slice(-1);
  return filename[0] === '.';
};

const byDirectoriesFirst = (a, b) => {
  if (a.isDirectory) {
    return -1;
  } else if (b.isDirectory) {
    return 1;
  } else {
    return 0;
  }
};

const readFile = filename => ({
  filename,
  hidden: isHidden(filename),
  isDirectory: isDirectory(filename),
  files:
    isDirectory(filename) &&
    fs
      .readdirSync(filename)
      .map(setBasePath(filename))
      .map(readFile)
      .filter(({ isHidden }) => !isHidden)
      .sort(byDirectoriesFirst)
      .reverse(),
});

// -----------------------------------------------------------------------------
// Main
// -----------------------------------------------------------------------------

const file = readFile('/path/to/dir');
printFile(file);