TheAlgorithms/JavaScript · error · TypeError

Invalid Triangle sides.

Error message

Invalid Triangle sides.

What it means

Thrown by areaTriangleWithAllThreeSides(side1, side2, side3) as a TypeError when the three given lengths violate the triangle inequality. The library enforces this before applying Heron's formula because Heron's formula would otherwise produce a NaN (square root of a negative product) for impossible triangles. The check is strict: a sum equal to the third side (degenerate triangle) is also rejected. This guard prevents silently returning mathematically meaningless results.

Source

Thrown at Maths/Area.js:93

 * @function areaTriangleWithAllThreeSides
 * @description Calculate the area of a triangle with the all three sides given.
 * @param {Integer} side1 - Integer
 * @param {Integer} side2 - Integer
 * @param {Integer} side3 - Integer
 * @return {Integer} - area of triangle.
 * @see [areaTriangleWithAllThreeSides](https://en.wikipedia.org/wiki/Heron%27s_formula)
 * @example areaTriangleWithAllThreeSides(5, 6, 7) = 14.7
 */
const areaTriangleWithAllThreeSides = (side1, side2, side3) => {
  validateNumericParam(side1, 'side1')
  validateNumericParam(side2, 'side2')
  validateNumericParam(side3, 'side3')
  if (
    side1 + side2 <= side3 ||
    side1 + side3 <= side2 ||
    side2 + side3 <= side1
  ) {
    throw new TypeError('Invalid Triangle sides.')
  }
  // Finding Semi perimeter of the triangle using formula
  const semi = (side1 + side2 + side3) / 2

  // Calculating the area of the triangle
  const area = Math.sqrt(
    semi * (semi - side1) * (semi - side2) * (semi - side3)
  )
  return Number(area.toFixed(2))
}

/**
 * @function areaParallelogram
 * @description Calculate the area of a parallelogram.
 * @param {Integer} base - Integer
 * @param {Integer} height - Integer
 * @return {Integer} - base * height
 * @see [areaParallelogram](https://en.wikipedia.org/wiki/Area#Dissection,_parallelograms,_and_triangles)

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Validate triangle inequality in your own code before calling: assert side1 + side2 > maxSide for each permutation of the three sides.
2. Inspect the raw inputs for zero, negative, or NaN values that may have slipped through validateNumericParam upstream.
3. If degenerate triangles (collinear points, zero area) are acceptable in your domain, wrap the call in try/catch and treat the failure as area 0.
4. Check that the three values correspond to the correct sides and were not transposed or duplicated during data binding.

Example fix

// before
const area = areaTriangleWithAllThreeSides(a, b, c) // throws if invalid

// after
function safeTriangleArea(s1, s2, s3) {
  const sides = [s1, s2, s3].sort((x, y) => x - y)
  if (sides[0] + sides[1] <= sides[2]) return 0 // degenerate or invalid
  return areaTriangleWithAllThreeSides(s1, s2, s3)
}

function canFormTriangle(s1, s2, s3) {
  const sides = [s1, s2, s3]
  // all must be positive numbers
  if (!sides.every(v => typeof v === 'number' && v > 0)) return false
  sides.sort((a, b) => a - b)
  return sides[0] + sides[1] > sides[2] // strict: degenerate rejected
}

if (!canFormTriangle(a, b, c)) {
  // skip or return 0; do not call areaTriangleWithAllThreeSides
}

function isValidTriangle(s1, s2, s3) {
  return [s1, s2, s3].every(v => typeof v === 'number' && Number.isFinite(v) && v > 0)
    && s1 + s2 > s3 && s1 + s3 > s2 && s2 + s3 > s1
}

try {
  const area = areaTriangleWithAllThreeSides(a, b, c)
} catch (e) {
  if (e instanceof TypeError && /Triangle sides/.test(e.message)) {
    // invalid triangle — treat as zero area or surface to caller
  } else throw e
}

When it happens

Trigger: Call areaTriangleWithAllThreeSides(1, 2, 10) where 1+2 <= 10; or any call where the largest side is greater than or equal to the sum of the other two (e.g. areaTriangleWithAllThreeSides(5, 5, 10) triggers because 5+5 <= 10). Passing zero-length sides where the inequality collapses (e.g. 0, 0, 5) also triggers it.

Common situations: User input collected from form fields arriving as strings parsed with parseInt but unvalidated for geometric feasibility; CSV/imported data with measurement errors or missing values represented as 0; unit-conversion mistakes (mm vs cm) making one side disproportionately large.

Related errors

• The ${paramName} only accepts non-negative values
• Input is not a valid 2D matrix.
• The two parameters must be distinct, non-null integers
• canvasWidth should be greater than zero
• The arg must be a valid, non empty string

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/8c546d2abbbf1aa6. Report an issue: GitHub.