antonmedv/fx · error · Error

Cannot sort ${typeof x}

Error message

Cannot sort ${typeof x}

What it means

sort(x) sorts in place and only accepts arrays; any other type throws 'Cannot sort <type>'. Strings, objects, numbers, null and undefined are all rejected — the library makes you convert explicitly rather than guessing a comparison order.

Source

Thrown at internal/engine/stdlib.js:40

  if (typeof fn === 'function') return fn(...args)
  return fn
}

function len(x) {
  if (Array.isArray(x)) return x.length
  if (typeof x === 'string') return x.length
  if (typeof x === 'object' && x !== null) return Object.keys(x).length
  throw new Error(`Cannot get length of ${typeof x}`)
}

function uniq(x) {
  if (Array.isArray(x)) return [...new Set(x)]
  throw new Error(`Cannot get unique values of ${typeof x}`)
}

function sort(x) {
  if (Array.isArray(x)) return x.sort()
  throw new Error(`Cannot sort ${typeof x}`)
}

function isFalsely(x) {
  return x === false || x === null || x === undefined
}

function filter(fn) {
  return function (x) {
    if (Array.isArray(x)) {
      return x.filter((v, i) => !isFalsely(fn(v, i)))
    }
    return isFalsely(fn(x)) ? skip : x
  }
}

function map(fn) {
  return function (x) {
    if (Array.isArray(x)) {

View on GitHub (pinned to 4f31cd3a0c)

Solutions

1. Verify with Array.isArray(x) before sorting and handle the non-array branch
2. For objects, sort keys instead: Object.keys(x).sort() or the library's sortKeys(x)
3. For strings, split into characters first: x.split('').sort().join('')
4. Default nullable values: sort(x ?? [])

Example fix

// before
const sorted = sort(cfg)
// after
const sorted = Array.isArray(cfg) ? sort(cfg) : sortKeys(cfg)

if (!Array.isArray(x)) throw new TypeError('sort() requires an array; got ' + (x === null ? 'null' : typeof x))

function isSortable(x) { return Array.isArray(x) }

let sorted; try { sorted = sort(x) } catch (e) { if (e.message.startsWith('Cannot sort')) { sorted = [] } else { throw e } }

When it happens

Trigger: sort('cba'), sort({a:1, b:2}), sort(null), sort(undefined), or sort applied to a pipeline value that is a scalar/object rather than an array.

Common situations: Sorting object keys by accident (need Object.keys(obj).sort() or sortKeys), sorting a string's characters (need split('') first), or sorting data that an upstream parse returned as null.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Cannot get length of ${typeof x}
• Cannot get unique values of ${typeof x}
• Cannot flatten ${typeof x}
• Cannot reverse ${typeof x}
• Cannot get keys of ${typeof x}

AI-assisted analysis of antonmedv/fx@4f31cd3a0c (2026-09-02). Data as JSON: /api/errors/5deab5c466c9a967. Report an issue: GitHub.