TheAlgorithms/JavaScript · error · Error

Number must be greater than zero.

Error message

Number must be greater than zero.

What it means

The hexagonalNumber function computes the nth hexagonal number via the formula n*(2n-1). Hexagonal numbers are a figurate sequence defined only for n >= 1; zero and negative indices have no valid representation. The guard at line 18 rejects any number <= 0 before computing.

Source

Thrown at Maths/HexagonalNumber.js:18

/*
 * Author: Akshay Dubey (https://github.com/itsAkshayDubey)
 * Hexagonal Number: https://en.wikipedia.org/wiki/Hexagonal_number
 * The nth hexagonal number hn is the number of distinct dots in a pattern of dots
 * consisting of the outlines of regular hexagons with sides up to n dots, when the
 * hexagons are overlaid so that they share one vertex.
 */

/**
 * @function hexagonalNumber
 * @description -> returns nth hexagonal number
 * @param {Integer} number
 * @returns {Integer} nth hexagonal number
 */

export const hexagonalNumber = (number) => {
  if (number <= 0) {
    throw new Error('Number must be greater than zero.')
  }
  return number * (2 * number - 1)
}

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Pass a positive integer (n >= 1) to hexagonalNumber.
2. If iterating from a 0-based index, add 1 before calling: hexagonalNumber(i + 1).
3. Validate user input is >= 1 before invoking the function.

Example fix

// before
for (let i = 0; i < 5; i++) {
  hexagonalNumber(i) // throws when i === 0
}
// after
for (let i = 1; i <= 5; i++) {
  hexagonalNumber(i)
}

if (!Number.isInteger(number) || number <= 0) {
  throw new RangeError('number must be a positive integer')
}
const result = hexagonalNumber(number)

const isPositiveInteger = (n) => typeof n === 'number' && Number.isInteger(n) && n > 0

When it happens

Trigger: Calling hexagonalNumber(0), hexagonalNumber(-1), or passing any non-positive value. A 0-based loop index fed directly into the function triggers it on the first iteration.

Common situations: Off-by-one loop starting at 0 instead of 1, using a 0-indexed array position as the figurate number argument, zero-defaulted variables, or user input parsed as 0.

Related errors

• Input data must be numbers
• Expected a valid real number
• Number must be greater than zero.
• Number must be greater than zero.
• Index cannot be Negative

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/0a9b3f198506e88a. Report an issue: GitHub.