TheAlgorithms/JavaScript · error · TypeError

Expected a valid real number

Error message

Expected a valid real number

What it means

The isDivisible function checks whether num1 is evenly divisible by num2. The guard rejects NaN, Infinity, and -Infinity for either argument using Number.isFinite, since divisibility is only defined for finite real numbers. Notably, division by zero returns false rather than throwing an error.

Source

Thrown at Maths/IsDivisible.js:5

// Checks if a number is divisible by another number.

export const isDivisible = (num1, num2) => {
  if (!Number.isFinite(num1) || !Number.isFinite(num2)) {
    throw new TypeError('Expected a valid real number')
  }
  if (num2 === 0) {
    return false
  }
  return num1 % num2 === 0
}

// isDivisible(10, 5) // returns true
// isDivisible(123498175, 5) // returns true
// isDivisible(99, 5) // returns false

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Validate both numbers are finite (Number.isFinite) before calling.
2. Sanitize parsed input that might be NaN before invoking.
3. Coerce or reject null/undefined values upstream.

Example fix

// before
isDivisible(parseFloat(str), 5)
// after
const n = Number(str)
if (!Number.isFinite(n)) return false
isDivisible(n, 5)

if (!Number.isFinite(num1) || !Number.isFinite(num2)) {
  return false
}
isDivisible(num1, num2)

const isFiniteNumber = (n) => typeof n === 'number' && Number.isFinite(n)

When it happens

Trigger: Calling isDivisible(NaN, 5), isDivisible(10, Infinity), or passing undefined/null (Number.isFinite returns false for both). Results of parseFloat on unparseable strings also trigger it.

Common situations: Passing results of parseFloat on bad input, unchecked arithmetic that produced Infinity, values from JSON that were null, or undefined from missing object properties.

Related errors

• Not a Number
• The two parameters must be distinct, non-null integers
• Arguments must be numbers
• Number must be greater than zero.
• Input data must be numbers

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/f527440fe57b2cff. Report an issue: GitHub.