index.js

/*jshint node:true*/
'use strict';

/**
 * Replaces characters in strings that are illegal/unsafe for filenames.
 * Unsafe characters are either removed or replaced by a substitute set
 * in the optional `options` object.
 *
 * Illegal Characters on vartious Operating Systems
 * / ? < > \ : * | "
 * https://kb.acronis.com/content/39790
 *
 * Unicode Control codes
 * C0 0x00-0x1f & C1 (0x80-0x9f)
 * http://en.wikipedia.org/wiki/C0_and_C1_control_codes
 *
 * Reserved filenames on Unix-based systems (".", "..")
 * Reserved filenames in Windows ("CON", "PRN", "AUX", "NUL", "COM1",
 * "COM2", "COM3", "COM4", "COM5", "COM6", "COM7", "COM8", "COM9",
 * "LPT1", "LPT2", "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", and
 * "LPT9") case-insesitively and with or without filename extensions.
 *
 * Capped at 255 characters in length.
 * http://unix.stackexchange.com/questions/32795/what-is-the-maximum-allowed-filename-and-folder-size-with-ecryptfs
 *
 * @param  {String} input   Original filename
 * @param  {Object} options {replacement: String | Function }
 * @return {String}         Sanitized filename
 */

const truncate = require('truncate-utf8-bytes');

const illegalRe = /[/?<>\\:*|"]/g;
const controlRe = /[\x00-\x1f\x80-\x9f]/g; //eslint-disable-line
const reservedRe = /^\.+$/;
const windowsReservedRe = /^(con|prn|aux|nul|com[0-9]|lpt[0-9])(\..*)?$/i; //eslint-disable-line
const windowsTrailingRe = /[. ]+$/;

function sanitize(input, { replacement, customIllegalChars }) {
  if (typeof input !== 'string') {
    throw new Error('Input must be string');
  }

  let sanitized = input
    .replace(illegalRe, replacement)
    .replace(controlRe, replacement)
    .replace(reservedRe, replacement)
    .replace(windowsReservedRe, replacement)
    .replace(windowsTrailingRe, replacement);

  if (customIllegalChars) {
    sanitized = sanitized.replace(
      new RegExp(customIllegalChars.join()), //eslint-disable-line
      replacement
    );
  }

  return truncate(sanitized, 255);
}

module.exports = function(input, options = {}) {
  options.replacement = (options && options.replacement) || '';

  const output = sanitize(input, options);
  if (options.replacement === '') {
    return output;
  }
  return sanitize(output, { replacement: '' });
};