isResultErr

Returns true for failed Result tuple

Usage

Check if a value is both a Result tuple and an Err result.

import * as 
import _
_ from 'radashi'

declare const 
const value: unknown
value: unknown

if (
import _
_.
function isResultErr<Error>(value: unknown): value is _.Err<Error>
Returns true if the value is an Err result.
@see ― https://radashi.js.org/reference/typed/isResultErr
@example 
isResultErr([new Error(), undefined]) // true
isResultErr([undefined, "hello"]) // false
@version ― 12.2.0
isResultErr(
const value: unknown
value)) {
  
const value: _.Err<Error>
value // <-- now an Err<Error> type
  
const value: _.Err<Error>
value[0] // <-- This is the error!
}

Also see the related isResult and isResultOk functions.