TheAlgorithms/JavaScript · error · TypeError

Argument should be string

Error message

Argument should be string

What it means

Atbash rejects any non-string input because it calls str.replace(/[a-z]/gi, ...). Passing a non-string would either coerce oddly or throw a less informative error from String.prototype.replace, so the guard validates up front.

Source

Thrown at Ciphers/Atbash.js:10

/**
 * @function Atbash - Decrypt a Atbash cipher
 * @description - The Atbash cipher is a particular type of monoalphabetic cipher formed by taking the alphabet and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on.
 * @param {string} str - string to be decrypted/encrypt
 * @return {string} decrypted/encrypted string
 * @see - [wiki](https://en.wikipedia.org/wiki/Atbash)
 */
const Atbash = (str) => {
  if (typeof str !== 'string') {
    throw new TypeError('Argument should be string')
  }

  return str.replace(/[a-z]/gi, (char) => {
    const charCode = char.charCodeAt()

    if (/[A-Z]/.test(char)) {
      return String.fromCharCode(90 + 65 - charCode)
    }

    return String.fromCharCode(122 + 97 - charCode)
  })
}

export default Atbash

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Pass a string: Atbash('secret').
2. Convert with String(value) or .toString() for non-string inputs.
3. Decode Buffers to utf8 before calling.

Example fix

// before
Atbash(12345)
// after
Atbash(String(12345))

function atbashSafe(v) {
  return Atbash(typeof v === 'string' ? v : String(v));
}

/** @param {unknown} s @returns {s is string} */
const isString = s => typeof s === 'string';

try { return Atbash(text); }
catch (e) {
  if (e instanceof TypeError && /should be string/.test(e.message)) {
    return Atbash(String(text));
  }
  throw e;
}

When it happens

Trigger: Passing a number, null, undefined, object, array, or Buffer instead of the text string.

Common situations: Encrypting a numeric ID without converting to string, or passing a Buffer from file/network input.

Related errors

• Argument str should be String
• Argument should be string
• Coefficient a, b should be number
• Arguments are invalid
• Arguments type are invalid

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/30705a464912d506. Report an issue: GitHub.