guard

144 bytes

Usage

The guard function allows you to make an async function return undefined if it rejects. This is useful when you want to handle errors in a functional way, such as returning a default value.

import * as _ from 'radashi'

const example = async () => {
  throw new Error()
}

const result = (await _.guard(example)) ?? []
// []

Guard only specific errors

The 2nd argument to guard is an error predicate. If provided, the function will only return undefined if the error matches the predicate.

import * as _ from 'radashi'

const DEFAULT_USER = { name: 'John Doe' }

async function fetchUser(id: string) {
  if (id === 'unknown') throw new Error('User does not exist')
  if (id === 'oops') throw new ReferenceError()
  return { name: 'Jim Jimmy' }
}

const isPlainError = (err: any) => err.name === 'Error'

const userA =
  (await _.guard(() => fetchUser('unknown'), isPlainError)) ?? DEFAULT_USER
// { name: "John Doe"}

// This one will reject.
const userB = await _.guard(() => fetchUser('oops'), isPlainError).catch(e => e)
// [object ReferenceError]

Synchronous guards

The guard function also works with synchronous functions.

import * as _ from 'radashi'

function example() {
  throw new Error()
}

const result = _.guard(example) ?? []
// []