Class Err<E>

constructor

• new Err<E>(error: E): Err<E>

  Type Parameters

  • E

  Parameters

  • error: E

  Returns Err<E>

Readonly_tag

[toStringTag]

• get "[toStringTag]"(): string

  Returns string

error

• get error(): E

  The error, if available.

  Returns E

value

• get value(): null

  The good value, if available.

  Returns null

[iterator]

• "[iterator]"(): IterableIterator<never>

  Returns IterableIterator<never>

and

• and<U>(other: Result<U, E>): Result<U, E>

  Returns the passed value if this is Ok, otherwise returns this.

  Type Parameters

  • U

  Parameters

  • other: Result<U, E>

  Returns Result<U, E>

andThen

• andThen<U, F = E>(fn: (value: never) => Result<U, F>): Err<E>

  Maps a Result<T, E> to Result<U, E | F> by applying a function to a contained Ok value, producing a new result.

  Type Parameters

  • U
  • F = E

  Parameters

  • fn: (value: never) => Result<U, F>

  Returns Err<E>

andThenAsync

• andThenAsync<U, F = E>(
      fn: (value: never) => Promise<Result<U, F>>,
  ): Promise<Err<E>>

  Maps a Result<T, E> to Promise<Result<U, E | F>> by applying a function to a contained Ok value, producing a new async result.

  Type Parameters

  • U
  • F = E

  Parameters

  • fn: (value: never) => Promise<Result<U, F>>

  Returns Promise<Err<E>>

err

• err(): Option<E>

  Returns an option of the inner error of a result.

  Returns Option<E>

expect

• expect(message: string): never

  Unwraps a result, yielding the value.

  USE THIS SPARINGLY! It is generally better to use unwrapOr or map to handle situations you may be temped to .expect() in.

  This is good for using in tests.

  Parameters

  • message: string

  Returns never

  Throws

  A new error with the provided message, if the result is an Err.

expectErr

• expectErr(message: string): E

  Unwraps a result, yielding the error.

  USE THIS SPARINGLY! It is generally better to use unwrapOr or map to handle situations you may be temped to .expect() in.

  This is good for using in tests.

  Parameters

  • message: string

  Returns E

  Throws

  A new error with the provided message, if the result is an Ok.

inspect

• inspect(): Err<E>

  Allows inspection of the interior result value, if it is Ok. May be useful in cases where you do not want to modify the result.

  Returns Err<E>

inspectErr

• inspectErr(fn: (error: E) => void): Err<E>

  Allows inspection of the interior error value, if it is Err. May be useful in cases where you do not want to modify the error.

  Parameters

  • fn: (error: E) => void

  Returns Err<E>

isErr

• isErr(): this is Err<E>

  Asserts that the current result is Err.

  Returns this is Err<E>

isErrAnd

• isErrAnd(fn: (error: E) => boolean): this is Err<E>

  Asserts that the current result is Err and the error passes the given predicate.

  Parameters

  • fn: (error: E) => boolean

  Returns this is Err<E>

isOk

• isOk(): this is Ok<never>

  Asserts that the current result is Ok.

  Returns this is Ok<never>

isOkAnd

• isOkAnd(fn: (value: never) => boolean): this is Ok<never>

  Asserts that the current result is Ok and the value passes the given predicate.

  Parameters

  • fn: (value: never) => boolean

  Returns this is Ok<never>

iter

• iter(): IterableIterator<never>

  Returns IterableIterator<never>

map

• map<U>(fn: (value: never) => U): Err<E>

  Maps a Result<T, E> to Result<U, E> by applying a function to a contained Ok value, leaving the Err value untouched.

  Type Parameters

  • U

  Parameters

  • fn: (value: never) => U

  Returns Err<E>

mapAsync

• mapAsync<U>(fn: (value: never) => Promise<U>): Promise<Err<E>>

  Maps a Result<T, E> to Promise<Result<U, E>> by applying a function to a contained Ok value, leaving the Err value untouched.

  Type Parameters

  • U

  Parameters

  • fn: (value: never) => Promise<U>

  Returns Promise<Err<E>>

mapErr

• mapErr<F>(fn: (error: E) => F): Err<F>

  Maps a Result<T, E> to Result<T, F> by applying a function to a contained Err value, leaving the Ok value untouched.

  Type Parameters

  • F

  Parameters

  • fn: (error: E) => F

  Returns Err<F>

mapOr

• mapOr<U>(fn: (value: never) => U, fallback: U): U

  Maps a Result<T, E> to U by applying a function to a contained Ok value. If the result is an Err, the fallback value will be returned.

  Type Parameters

  • U

  Parameters

  • fn: (value: never) => U
  • fallback: U

  Returns U

mapOrAsync

• mapOrAsync<U>(fn: (value: never) => Promise<U>, fallback: U): Promise<U>

  Maps a Result<T, E> to Promise by applying a function to a contained Ok value. If the result is an Err, the fallback value will be returned.

  Type Parameters

  • U

  Parameters

  • fn: (value: never) => Promise<U>
  • fallback: U

  Returns Promise<U>

mapOrElse

• mapOrElse<U>(fn: (value: never) => U, fallback: () => U): U

  Maps a Result<T, E> to U by applying a function to a contained Ok value. If the result is an Err, the fallback function will be called and its result will be returned.

  Type Parameters

  • U

  Parameters

  • fn: (value: never) => U
  • fallback: () => U

  Returns U

mapOrElseAsync

• mapOrElseAsync<U>(
      fn: (value: never) => Promise<U>,
      fallback: () => Promise<U>,
  ): Promise<U>

  Maps a Result<T, E> to Promise by applying a function to a contained Ok value. If the result is an Err, the fallback function will be called and its result will be returned.

  Type Parameters

  • U

  Parameters

  • fn: (value: never) => Promise<U>
  • fallback: () => Promise<U>

  Returns Promise<U>

ok

• ok(): Option<never>

  Returns an option of the inner value of a result.

  Returns Option<never>

or

• or<U, F>(result: Result<U, F>): Result<U, F>

  Returns the passed value if this is Err, otherwise returns this.

  Type Parameters

  • U
  • F

  Parameters

  • result: Result<U, F>

  Returns Result<U, F>

orElse

• orElse<U, F>(fn: (error: E) => Result<U, F>): Result<U, F>

  Calls fn if the result is an Err, otherwise returns this.

  Type Parameters

  • U
  • F

  Parameters

  • fn: (error: E) => Result<U, F>

  Returns Result<U, F>

toString

• toString(): string

  Returns a string representation of the result for debugging purposes.

  Returns string

unwrap

• unwrap(): never

  Returns the inner value of a result, if it is Ok. Otherwise, the contained error will be thrown.

  USE THIS SPARINGLY! It is generally better to use unwrapOr or map to handle situations you may be temped to .unwrap() in.

  Returns never

  Throws

  The contained error, if the result is an Err.

unwrapOr

• unwrapOr<V>(fallback: V): V

  Returns the inner value of a result, if it is Ok. Otherwise, the provided fallback value will be returned.

  Type Parameters

  • V

  Parameters

  • fallback: V

  Returns V

unwrapOrElse

• unwrapOrElse<V>(fn: () => V): V

  Returns the inner value of a result, if it is Ok. Otherwise, the provided fallback funtion will be called and its result will be returned.

  Type Parameters

  • V

  Parameters

  • fn: () => V

  Returns V