@cometloop/safe - Type-safe error handling with the Result pattern for TypeScript.

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safe.wrap

Wraps a synchronous function so it returns a [data, error] tuple instead of throwing.

import { safe } from '@cometloop/safe'

const parseJson = (input: string) => {
  return JSON.parse(input)
}

const safeParseJson = safe.wrap(parseJson)

const [data, error] = safeParseJson('{"name": "Alice", "age": 30}')

if (error) {
  console.log('Parse failed:', error.message)
} else {
  console.log('Parsed:', data)
}

Controls

JSON

Output

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safe.wrapAsync

Wraps an async function so it returns a Promise<[data, error]> tuple instead of rejecting.

import { safe } from '@cometloop/safe'

// Toggle this to simulate success or failure
const shouldFail = false

const fetchUser = async () => {
  return new Promise<{ id: number; name: string }>((resolve, reject) => {
    setTimeout(() => {
      if (shouldFail) {
        reject(new Error('Network timeout'))
      } else {
        resolve({ id: 1, name: 'Alice' })
      }
    }, 1000)
  })
}

const safeFetchUser = safe.wrapAsync(fetchUser)

const [user, error] = await safeFetchUser()

if (error) {
  console.log('Fetch failed:', error.message)
} else {
  console.log('User:', user)
}

Controls

Output

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safe.wrap with args

Wrapped functions forward arguments and preserve type safety on inputs and outputs.

import { safe } from '@cometloop/safe'

const divide = (a: number, b: number) => {
  if (b === 0) throw new Error('Division by zero')
  return a / b
}

const safeDivide = safe.wrap(divide)

const [result, error] = safeDivide(10, 2)

if (error) {
  console.log('Error:', error.message)
} else {
  console.log('Result:', result) // 5
}

Controls

Output

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safe.wrapAsync with args

Wrapped async functions forward arguments and preserve type safety on inputs and outputs.

import { safe } from '@cometloop/safe'

// Toggle this to simulate a server error
const shouldFail = false

const fetchUser = async (id: string) => {
  return new Promise<{ id: string; name: string; email: string }>(
    (resolve, reject) => {
      setTimeout(() => {
        if (shouldFail) {
          reject(new Error('HTTP 500'))
        } else {
          resolve({ id, name: 'Alice', email: 'alice@example.com' })
        }
      }, 800)
    }
  )
}

const safeFetchUser = safe.wrapAsync(fetchUser)

const [user, error] = await safeFetchUser('42')

if (error) {
  console.log('Fetch failed:', error.message)
} else {
  console.log('User:', user)
}

Controls

User IDSimulate server error

Output

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