Class Result<T, E>

The Result type is an immutable representation of either success (Ok) or failure (Err).

Type Parameters

T = any
E = any

Methods

[iterator]

[iterator](): Generator<T, void, unknown>
Returns an iterator over the possibly contained value.

The iterator yields one value if the result is Ok, otherwise none.

Returns Generator<T, void, unknown>
- Defined in result.ts:149

and

and<BT, BE>(resultB): Result<BT, E | BE>
Type Parameters
- BT
- BE = any
Parameters
- resultB: Result<BT, BE>
Returns Result<BT, E | BE>
- Defined in result.ts:197

andThen

andThen<BT, BE>(getResultB, thisArg?): Result<BT, E | BE>
Type Parameters
- BT
- BE = any
Parameters
- getResultB: ((value: T) => Result<BT, BE>)
 A function that returns a Result
 - - (value): Result<BT, BE>
 - Parameters
 value: T
 Returns Result<BT, BE>
- OptionalthisArg: any
 If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns Result<BT, E | BE>
Err if the Result is Err, otherwise calls getOptionB with the wrapped value and returns the result.
- Defined in result.ts:207

err

err(): Option<E>
Converts from Result<T, E> to Option<E> and discarding the value, if any.

Returns Option<E>
- Defined in result.ts:302

flatten

flatten(): Result<UnwrapOk<T, T>, E | UnwrapErr<E, E>>
Converts from Option<Option<T>> to Option<T>

Returns Result<UnwrapOk<T, T>, E | UnwrapErr<E, E>>
- Defined in result.ts:243

isErr

isErr(): boolean
Returns boolean
true if the Result is an Err.
- Defined in result.ts:165

isErrAnd

isErrAnd(predicate, thisArg?): boolean
Parameters
- predicate: ((error: E) => boolean)
  - - (error): boolean
    - Parameters
      error: E
      Returns boolean
- OptionalthisArg: any
  If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns boolean
true if the Result is an Err and and the error inside of it matches a predicate.
- Defined in result.ts:181

isOk

isOk(): boolean
Returns boolean
true if the Result is an Ok.
- Defined in result.ts:158

isOkAnd

isOkAnd(predicate, thisArg?): boolean
Parameters
- predicate: ((value: T) => boolean)
  - - (value): boolean
    - Parameters
      value: T
      Returns boolean
- OptionalthisArg: any
  If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns boolean
true if the Result is an Ok and and the value inside of it matches a predicate.
- Defined in result.ts:173

isSame

isSame(other): boolean
Whether this Ok value or Err error is the same as the other Result.
Parameters
- other: unknown
  Another Result or any value
Returns boolean
true if the other is an Result and the Ok value or Err error is the same as this via Object.is.
- Defined in result.ts:191

map

map(fn, thisArg?): Result<U, E>
Maps an Result<T, E> to Result<U, E> by applying a function to a contained Ok value, leaving an Err value untouched.
Type Parameters
- U
Parameters
- fn: ((value: T) => U)
 A function that maps a value to another value
 - - (value): U
 - Parameters
 value: T
 Returns U
- OptionalthisArg: any
 If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns Result<U, E>
Err if the Result is Err, otherwise returns Ok(fn(value)).
- Defined in result.ts:256

mapErr

mapErr(fn, thisArg?): Result<T, U>
Maps a Result<T, E> to Result<T, F> by applying a function to a contained Err value, leaving an Ok value untouched.

This function can be used to pass through a successful result while handling an error.
Type Parameters
- U
Parameters
- fn: ((error: E) => U)
 A function that maps a error to another error
 - - (error): U
 - Parameters
 error: E
 Returns U
- OptionalthisArg: any
 If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns Result<T, U>
Ok if the Result is Ok, otherwise returns Err(fn(error)).
- Defined in result.ts:271

match

match(Ok, Err): U
Extract the value from an Result in a way that handles both the Ok and Err cases.
Type Parameters
- U
Parameters
- Ok: ((value: T) => U)
  A function that returns a value if the Result is a Ok.
  - - (value): U
    - Parameters
      value: T
      Returns U
- Err: ((error: E) => U)
  A function that returns a value if the Result is a Err.
  - - (error): U
    - Parameters
      error: E
      Returns U
Returns U
The value returned by the provided function.
- Defined in result.ts:395

ok

ok(): Option<T>
Converts from Result<T, E> to Option<T> and discarding the error, if any.

Returns Option<T>
- Defined in result.ts:295

or

or<BT, BE>(resultB): Result<T | BT, E | BE>
Type Parameters
- BT
- BE = any
Parameters
- resultB: Result<BT, BE>
 A Result
Returns Result<T | BT, E | BE>
the Result if it is Ok, otherwise returns resultB.

Arguments passed to or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use orElse, which is lazily evaluated.
- Defined in result.ts:223

orElse

orElse<BT, BE>(getResultB, thisArg?): Result<T | BT, E | BE>
Type Parameters
- BT
- BE = any
Parameters
- getResultB: (() => Result<BT, BE>)
 A function that returns an Result
 - - (): Result<BT, BE>
 - Returns Result<BT, BE>
- OptionalthisArg: any
 If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns Result<T | BT, E | BE>
the Result if it contains a value, otherwise calls getResultB and returns the result.
- Defined in result.ts:233

toString

toString(): string
Returns string
- Defined in result.ts:399

transpose

transpose(): Option<Result<UnwrapOption<T>, E>>
Transposes a Result(Option) into Option(Result).
- Ok(Some(_)) will be mapped to `Some(Ok(_))
- Err(_) will be mapped to Some(Err(_)).
- Ok(_) will be mapped to Some(Ok(_)).
Returns Option<Result<UnwrapOption<T>, E>>
- Defined in result.ts:284

unwrap

unwrap(message?): T
Parameters
- message: string = "called `Result.unwrap()` on an `Err`"
  Optional Error message
Returns T
the contained Ok value.

Throws
if the value is an Err.
- Defined in result.ts:313

unwrapErr

unwrapErr(message?): E
Parameters
- message: string = "called `Result.unwrapErr()` on an `Ok` value"
  Optional Error message
Returns E
the contained Err error.

Throws
if the error is an Ok.
- Defined in result.ts:352

unwrapErrOr

unwrapErrOr(): undefined | E
Returns undefined | E
the contained Err error or undefined otherwise.

Arguments passed to unwrapErrOr are eagerly evaluated; if you are passing the result of a function call, it is recommended to use unwrapErrOrElse, which is lazily evaluated.
- Defined in result.ts:366
unwrapErrOr(defaultError): E | U
Type Parameters
- U
Parameters
- defaultError: U
  default error
Returns E | U
the contained Err error or a provided default.

Arguments passed to unwrapErrOr are eagerly evaluated; if you are passing the result of a function call, it is recommended to use unwrapErrOrElse, which is lazily evaluated.
- Defined in result.ts:374

unwrapErrOrElse

unwrapErrOrElse(fn, thisArg?): E | U
Type Parameters
- U
Parameters
- fn: (() => U)
  A function that computes a default value.
  - - (): U
    - Returns U
- OptionalthisArg: any
  If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns E | U
the contained Err error or computes it from a closure.
- Defined in result.ts:384

unwrapOr

unwrapOr(): undefined | T
Returns undefined | T
the contained Ok value or undefined otherwise.
- Defined in result.ts:323
unwrapOr(defaultValue): T | U
Type Parameters
- U
Parameters
- defaultValue: U
  default value
Returns T | U
the contained Ok value or a provided default.

Arguments passed to unwrapOr are eagerly evaluated; if you are passing the result of a function call, it is recommended to use unwrapOrElse, which is lazily evaluated.
- Defined in result.ts:331

unwrapOrElse

unwrapOrElse(fn, thisArg?): T | U
Type Parameters
- U
Parameters
- fn: (() => U)
  A function that computes a default value.
  - - (): U
    - Returns U
- OptionalthisArg: any
  If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns T | U
the contained Ok value or computes it from a closure.
- Defined in result.ts:341

`Static` `Readonly`Err

Err<E, T>(error): Result<T, E>
Type Parameters
- E
- T = any
Parameters
- error: E
 An error of type E
Returns Result<T, E>
Wrap an error into an Result.
- Defined in result.ts:30

`Static`from

from<T, E>(source): Result<T, E>
Err if the value is an Error.
Type Parameters
- T = any
- E extends Error = Error
Parameters
- source: T | E
Returns Result<T, E>
- Defined in result.ts:38
from<T, E>(source, predicate, thisArg?): Result<T, E>
OK if the value satisfies the predicate, otherwise Err
Type Parameters
- T = any
- E = any
Parameters
- source: T | E
 Source value
- predicate: ((source: T | E) => source is T)
 A function that returns true if the value satisfies the predicate, otherwise false
 - - (source): source is T
 - Parameters
 source: T | E
 Returns source is T
- OptionalthisArg: any
 If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns Result<T, E>
- Defined in result.ts:48
from<T, E>(source, predicate, thisArg?): Result<T, E>
OK if the value satisfies the predicate, otherwise Err
Type Parameters
- T = any
- E = any
Parameters
- source: T | E
 Source value
- predicate: ((source: T | E) => boolean)
 A function that returns true if the value satisfies the predicate, otherwise false
 - - (source): boolean
 - Parameters
 source: T | E
 Returns boolean
- OptionalthisArg: any
 If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns Result<T, E>
- Defined in result.ts:60

`Static`isResult

isResult<T, E>(maybeResult): maybeResult is Result<T, E>
Type Parameters
- T
- E
Parameters
- maybeResult: unknown
 A value that might be an Result
Returns maybeResult is Result<T, E>
true if the given value is an Result.
- Defined in result.ts:114

`Static`isSame

isSame(a, b): boolean
Parameters
- a: unknown
  An Result or any value
- b: unknown
  An Result or any value
Returns boolean
true if the both are Result and the Ok value or Err error are the same via Object.is.
- Defined in result.ts:128

`Static` `Readonly`Ok

Ok<T, E>(value): Result<T, E>
Type Parameters
- T
- E = any
Parameters
- value: T
 A value of type T
Returns Result<T, E>
Wrap a value into an Result.
- Defined in result.ts:23

`Static`try

try<T, E, TArgs>(fn, ...args): Result<T, E>
Ok if the fn returns a value, Err if the fn throws.
Type Parameters
- T = any
- E = any
- TArgs extends any[] = []
Parameters
- fn: ((...args: TArgs) => T)
 - - (...args): T
 - Parameters
 Rest...args: TArgs
 Returns T
- Rest...args: TArgs
Returns Result<T, E>
Ok with the returned value or Err with the exception error.
- Defined in result.ts:82

`Static`tryAsync

tryAsync<T, E, TArgs>(fn, ...args): Promise<Result<T, E>>
Ok if the fn returned Promise resolves a value, Err if the fn throws or the Promise rejected.
Type Parameters
- T = any
- E = any
- TArgs extends any[] = []
Parameters
- fn: ((...args: TArgs) => T)
 - - (...args): T
 - Parameters
 Rest...args: TArgs
 Returns T
- Rest...args: TArgs
Returns Promise<Result<T, E>>
Ok with the resolved value or Err with the exception error or the rejected value.
- Defined in result.ts:98

Class Result<T, E>

Type Parameters

Index

Methods

Methods

[iterator]

Returns Generator<T, void, unknown>

and

Type Parameters

Parameters

Returns Result<BT, E | BE>

andThen

Type Parameters

Parameters

Parameters

Returns Result<BT, BE>

Returns Result<BT, E | BE>

err

Returns Option<E>

flatten

Returns Result<UnwrapOk<T, T>, E | UnwrapErr<E, E>>

isErr

Returns boolean

isErrAnd

Parameters

Parameters

Returns boolean

Returns boolean

isOk

Returns boolean

isOkAnd

Parameters

Parameters

Returns boolean

Returns boolean

isSame

Parameters

Returns boolean

map

Type Parameters

Parameters

Parameters

Returns U

Returns Result<U, E>

mapErr

Type Parameters

Parameters

Parameters

Returns U

Returns Result<T, U>

match

Type Parameters

Parameters

Parameters

Returns U

Parameters

Returns U

Returns U

ok

Returns Option<T>

or

Type Parameters

Parameters

Returns Result<T | BT, E | BE>

orElse

Type Parameters

Parameters

Returns Result<BT, BE>

Returns Result<T | BT, E | BE>

toString

Returns string

transpose

Returns Option<Result<UnwrapOption<T>, E>>

unwrap

Parameters

Returns T

Throws

unwrapErr

Parameters

Returns E

`Static` `Readonly`Err

`Static`from

`Static`isResult

`Static`isSame

`Static` `Readonly`Ok

`Static`try

`Static`tryAsync