TheAlgorithms/JavaScript · error · Error

Input is not a valid 2D matrix.

Error message

Input is not a valid 2D matrix.

What it means

Thrown by determinant(matrix) (Determinant.js:58) as a plain Error when the input is not structurally a 2D array: it fails Array.isArray on the outer value, or the outer array is empty, or the first row (matrix[0]) is not itself an array. This is the structural validation that runs before the squareness check. Passing a 1D array like [1,2,3] triggers it because matrix[0] is a number, not an array.

Source

Thrown at Maths/Determinant.js:59

}

const isMatrixSquare = (matrix) => {
  let numRows = matrix.length
  for (let i = 0; i < numRows; i++) {
    if (numRows !== matrix[i].length) {
      return false
    }
  }
  return true
}

const determinant = (matrix) => {
  if (
    !Array.isArray(matrix) ||
    matrix.length === 0 ||
    !Array.isArray(matrix[0])
  ) {
    throw new Error('Input is not a valid 2D matrix.')
  }
  if (!isMatrixSquare(matrix)) {
    throw new Error('Square matrix is required.')
  }
  let numCols = matrix[0].length
  if (numCols === 1) {
    return matrix[0][0]
  }
  let result = 0
  let setIndex = 0
  for (let i = 0; i < numCols; i++) {
    result +=
      Math.pow(-1, i) *
      matrix[setIndex][i] *
      determinant(subMatrix(matrix, setIndex, i))
  }
  return result
}

View on GitHub (pinned to 5c39e87a9a)

Solutions

1. Ensure the input is an array of arrays: Array.isArray(m) && Array.isArray(m[0]).
2. Convert flat data to 2D before calling, e.g. chunk into rows of equal length.
3. If using typed arrays, convert with Array.from before passing.
4. Guard against empty input at the boundary and return a sensible default.

Example fix

// before
const d = determinant(flatArray) // flatArray is [1,2,3,4]

// after
function toMatrix(flat, cols) {
  return Array.from({ length: flat.length / cols }, (_, i) =>
    flat.slice(i * cols, i * cols + cols))
}
const d = determinant(toMatrix(flatArray, 2))

if (!Array.isArray(matrix) || matrix.length === 0 || !Array.isArray(matrix[0])) {
  throw new Error('input must be a non-empty 2D array')
}
const d = determinant(matrix)

const is2DArray = (v) => Array.isArray(v) && v.length > 0 && v.every(row => Array.isArray(row))

try {
  d = determinant(matrix)
} catch (e) {
  if (e instanceof Error && /not a valid 2D matrix/.test(e.message)) {
    // not 2D — convert or reject
  } else throw e
}

When it happens

Trigger: Call determinant([1, 2, 3]) passing a flat array; determinant([]) passing an empty array; determinant('matrix') or determinant(null) passing a non-array; determinant([[1,2],[3,4,5]]) does NOT throw here (it is structurally 2D) but would fail the squareness check next.

Common situations: Flattening a matrix by mistake; receiving a vector instead of a matrix from an upstream op; empty result from a data loader; passing a typed array (Int32Array) which is not Array.isArray.

Related errors

• Square matrix is required.
• Input is not a valid 2D matrix.
• Invalid Triangle sides.
• Invalid Input
• Index out of range

AI-assisted analysis of TheAlgorithms/JavaScript@5c39e87a9a (2026-08-13). Data as JSON: /api/errors/f4918540ed837ab1. Report an issue: GitHub.