TheAlgorithms/JavaScript · error · TypeError

Arguments are invalid

Error message

Arguments are invalid

What it means

Caesar cipher rejects the call when str is not a string OR rotation is not an integer OR rotation is negative. The three conditions are checked in one combined guard, so the message does not say which argument failed; all three must be valid (string + non-negative integer).

Source

Thrown at Ciphers/CaesarCipher.js:11

/**
 * @function caesarsCipher
 * @description - In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.
 * @see - [wiki](https://en.wikipedia.org/wiki/Caesar_cipher)
 * @param  {string} str - string to be encrypted
 * @param {number} rotation - the number of rotation, expect real number ( > 0)
 * @return {string} - decrypted string
 */
const caesarCipher = (str, rotation) => {
  if (typeof str !== 'string' || !Number.isInteger(rotation) || rotation < 0) {
    throw new TypeError('Arguments are invalid')
  }

  const alphabets = new Array(26)
    .fill()
    .map((_, index) => String.fromCharCode(97 + index)) // generate all lower alphabets array a-z

  const cipherMap = alphabets.reduce(
    (map, char, index) => map.set(char, alphabets[(rotation + index) % 26]),
    new Map()
  )

  return str.replace(/[a-z]/gi, (char) => {
    if (/[A-Z]/.test(char)) {
      return cipherMap.get(char.toLowerCase()).toUpperCase()
    }

    return cipherMap.get(char)
  })

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Pass a string and a non-negative integer: caesarCipher('abc', 3).
2. Parse rotation: Math.abs(Math.trunc(Number(raw))).
3. Split-validate each argument before calling if you need a specific error message.

Example fix

// before
caesarCipher(text, argv.shift) // string rotation
// after
const shift = Math.abs(Math.trunc(Number(argv.shift)))
caesarCipher(String(text), shift)

function caesarSafe(text, raw) {
  const rot = Math.abs(Math.trunc(Number(raw)));
  return caesarCipher(String(text), Number.isInteger(rot) ? rot : 0);
}

/** @param {string} s @param {unknown} r @returns {boolean} */
const validCaesarArgs = (s, r) => typeof s === 'string' && Number.isInteger(r) && r >= 0;

try { return caesarCipher(text, rotation); }
catch (e) {
  if (e instanceof TypeError && /Arguments are invalid/.test(e.message)) {
    return caesarCipher(String(text), Math.abs(Math.trunc(Number(rotation))));
  }
  throw e;
}

When it happens

Trigger: str is a number/object, rotation is a float (3.5), a string ("3"), negative (-1), NaN, or undefined.

Common situations: Reading rotation from input/argv as a string, allowing a user-controlled negative shift, or omitting the rotation argument.

Related errors

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

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/640162b7292d4354. Report an issue: GitHub.