Generates a random string with a given lenth

generateRandomString.js

/**
 * Generate a random string with a given lenth
 *
 * @author <@thehomelessdev>
 * @version 1.0.1
 *
 * @example
 * // returns ten random characters including numbers and special characters
 * generateRandomString(10, { includeSpecialCharacters: true })
 *
 * @param {number} len number of characters to include in the result
 * @param {object} options controls output
 *        @param[0] {boolean}  includeSpecialCharacters If true include special
 *                             characters
 *        @param[1] {boolean}  includeNumbers If true include numbers
 *
 * @returns {string}
 */
const generateRandomString = (len, options: { includeSpecialCharacters = false, includeNumbers = true }) => {
  // extract options with default values
  const { includeSpecialCharacters = false, includeNumbers = true } = options
  
  // possible numbers
  const _numbers = "0123456789";
  
  // possible special characters (feel free to add whatever special character
  // you need
  const _specialChars = `!*@.,;:-_+/'?"!|`;
  
  // All possible characters (add _numbers and _specialChars depending on the options)
  const _sym = `ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz${includeNumbers ? _numbers : ""}${includeSpecialCharacters ? _specialChars : ""}`;
  
  // Initialize result variable as an empty string
  let str = "";

  // for each time between 0 and the passed length append one of the
  // available characters
  for (let i = 0; i < len; i++) {
    // Math.floor() rounds down and returns the largest integer less than
    // or equal to a given number (Math.random() * _sym.length)
    // Math.random() return a random float number between 0 and 1 which
    // multiply by _sym.length, basicaly selects a random character within _sym.
    str += _sym.charAt(Math.floor(Math.random() * _sym.length));
  }

  return str;
};