TheAlgorithms/JavaScript · error · RangeError

Input should be a non-negative whole number

Error message

Input should be a non-negative whole number

What it means

Thrown by `factorial(n)` (recursive) when `!Number.isInteger(n) || n < 0`. This is a `RangeError` (not TypeError), and it correctly catches NaN, floats, negatives, and non-numbers in one check because `Number.isInteger` is false for all of those. This is the most thorough input guard in the set.

Source

Thrown at Recursive/Factorial.js:13

/**
 * @function Factorial
 * @description function to find factorial using recursion.
 * @param {Integer} n - The input integer
 * @return {Integer} - Factorial of n.
 * @see [Factorial](https://en.wikipedia.org/wiki/Factorial)
 * @example 5! = 1*2*3*4*5 = 120
 * @example 2! = 1*2 = 2
 */

const factorial = (n) => {
  if (!Number.isInteger(n) || n < 0) {
    throw new RangeError('Input should be a non-negative whole number')
  }

  if (n === 0) {
    return 1
  }

  return n * factorial(n - 1)
}

export { factorial }

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Validate `Number.isInteger(n) && n >= 0` upstream (matches the function's own guard).
2. Coerce integer-like strings with `Number(n)` and check `Number.isInteger`.
3. For large n, prefer an iterative factorial to avoid stack overflow - the recursive version has no guard against deep recursion.

Example fix

// before
factorial(userInput) // userInput could be -1 or 3.5

// after
const n = Number(userInput)
if (!Number.isInteger(n) || n < 0) throw new RangeError('n must be a non-negative integer')
factorial(n)

const n = Number(input)
if (!Number.isInteger(n) || n < 0) {
  throw new RangeError('n must be a non-negative integer')
}
factorial(n)

const isNonNegativeInt = (x) => typeof x === 'number' && Number.isInteger(x) && x >= 0

When it happens

Trigger: Call `factorial(-1)`, `factorial(3.5)`, `factorial(NaN)`, `factorial('5')`, `factorial(undefined)`, `factorial(Infinity)`. All non-negative integers (including 0, which returns 1) pass.

Common situations: Floating-point math producing a non-integer by accident, negative numbers from sign errors, or unguarded user input.

Related errors

• The ${noName} only accepts positive values
• No natural numbers exist below 1
• Fibonacci sequence limit can't be less than 1
• Error size should be less than equal to 32
• Capacity should be greater than 0

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/bc851587b27700ea. Report an issue: GitHub.