Class Result<T, E>

A type which represents values that may encode either a successful result or an error result.

Type Parameters

T extends NonNullable<unknown>
the type of successful results
E extends NonNullable<unknown> = Error
the type of error results

Index

Boolean operators

and

and(this: Result<T, E>, other: Result<U, E>): Result<U, E>
Takes another Result and returns it if this is Ok, otherwise returns this.
Type Parameters
- U extends {}
 the type contained in the Result returned by fn
Parameters
- this: Result<T, E>
- other: Result<U, E>
 a Result to return if this is Ok
Returns Result<U, E>
other if this is Ok, this otherwise
See
- andThen
- andThenAsync
- or
- orElse
- orElseAsync
- Defined in result.ts:285

andThen

andThen(
this: Result<T, E>,
fn: (value: T) => Result<U, E>,
): Result<U, E>
Takes a function which takes the value contained in this and returns a new Result; calls it and returns the result if this is Ok, otherwise returns this. Also sometimes known in other languages or libraries as flatmap or bind.
Type Parameters
- U extends {}
 the type contained in the Result returned by fn
Parameters
- this: Result<T, E>
- fn: (value: T) => Result<U, E>
 a function that will be called with the value in this if this is Ok
Returns Result<U, E>
the result of calling fn if this is Ok, this otherwise
See
- and
- andThenAsync
- or
- orElse
- orElseAsync
- Defined in result.ts:261

andThenAsync

andThenAsync(
this: Result<T, E>,
fn: (value: T) => Promise<Result<U, E>>,
): Promise<Result<U, E>>
Takes a function which takes the value contained in this and returns a promise which resolves to a new Result; calls it and returns the result if this is Ok, otherwise returns a promise which resolves to this. This is an async version of andThen.
Type Parameters
- U extends {}
 the type contained in the Result returned by fn
Parameters
- this: Result<T, E>
- fn: (value: T) => Promise<Result<U, E>>
 a function that will be called with the value in this if this is Ok
Returns Promise<Result<U, E>>
the result of calling fn if this is Ok, this otherwise
See
- and
- andThen
- or
- orElse
- orElseAsync
- Defined in result.ts:309

or

or<F extends {} = Error>(this: Result<T, E>, other: Result<T, F>): Result<T, F>
Takes another Result and returns it if this is Err, otherwise returns this.
Type Parameters
- F extends {} = Error
Parameters
- this: Result<T, E>
- other: Result<T, F>
 a Result to return if this is Err
Returns Result<T, F>
other if this is Err, this otherwise
See
- and
- andThen
- andThenAsync
- orElse
- orElseAsync
- Defined in result.ts:357

orElse

orElse<F extends {} = Error>(
this: Result<T, E>,
fn: (error: E) => Result<T, F>,
): Result<T, F>
Takes a function which takes an error and returns a Result; calls it on the contained error and returns the result if this is Err, otherwise returns this.
Type Parameters
- F extends {} = Error
Parameters
- this: Result<T, E>
- fn: (error: E) => Result<T, F>
 a function that will be called with the error value if this is Err
Returns Result<T, F>
the result of calling fn if this is Err, this otherwise
See
- and
- andThen
- andThenAsync
- or
- orElseAsync
- Defined in result.ts:334

orElseAsync

orElseAsync<F extends {} = Error>(
this: Result<T, E>,
fn: (error: E) => Promise<Result<T, F>>,
): Promise<Result<T, F>>
Takes a function which takes an error and returns a promise which resolves to a new Result; calls it with the contained error and returns the result if this is Err, otherwise returns a promise which resolves to this.
Type Parameters
- F extends {} = Error
Parameters
- this: Result<T, E>
- fn: (error: E) => Promise<Result<T, F>>
 a function that will be called if this is Err
Returns Promise<Result<T, F>>
the result of calling fn if this is Err, this otherwise
See
- and
- andThen
- andThenAsync
- or
- orElse
- Defined in result.ts:379

Constructing

`Static`Err

Err<T extends {}, E extends {} = Error>(error: E): Result<T, E>
Construct a Result containing an error value.
Type Parameters
- T extends {}
 the type of success values
- E extends {} = Error
 the type of the error value
Parameters
- error: E
 the error contained by the Result
Returns Result<T, E>
a Result containing an error error
See
- Ok
- wrap
- wrapAsync
- Defined in result.ts:59

`Static`Ok

Ok<T extends {}, E extends {} = Error>(value: T): Result<T, E>
Construct a Result containing a success value.
Type Parameters
- T extends {}
 the type of the value
- E extends {} = Error
 the type of error results
Parameters
- value: T
 the value contained by the Result
Returns Result<T, E>
a Result containing value
See
- Err
- wrap
- wrapAsync
- Defined in result.ts:40

`Static`wrap

wrap<T extends {}>(fn: () => T): Result<T, Option<{}>>
Takes a function that could be throw and converts it into an Result.
Type Parameters
- T extends {}
 the type contained by the Result
Parameters
- fn: () => T
 the function which could throw
Returns Result<T, Option<{}>>
Ok with the return value of fn if fn doesn't throw, otherwise Err containing an Option which is None if the exception is null or undefined, and is Some with the exception otherwise
See
- Ok
- Err
- wrapAsync
- Defined in result.ts:116

`Static`wrapAsync

wrapAsync<T extends {}>(promise: Promise<T>): Promise<Result<T, Option<{}>>>
Takes a promise that could reject and converts it into an Result.
Type Parameters
- T extends {}
 the type contained by the Result
Parameters
- promise: Promise<T>
 the promise to convert
Returns Promise<Result<T, Option<{}>>>
a Promise containing Ok with the value resolved by promise if promise doesn't reject, otherwise Err containing an Option which is None if promise rejects with a null or undefined, and is Some with the rejection value otherwise
See
- Ok
- Err
- wrap
- Defined in result.ts:141

Extracting the contained value

match

match(
this: Result<T, E>,
matchers: { Err: (error: E) => U; Ok: (value: T) => U },
): U
Takes two functions, one is called with the contained value if this is Ok and the other is called with the error if this is Err.
Type Parameters
- U
 the type of the return value of the matcher functions
Parameters
- this: Result<T, E>
- matchers: { Err: (error: E) => U; Ok: (value: T) => U }
 an object containing matcher functions
 - Err: (error: E) => U
 A function that will be called on the value contained if this is Err.
 - Ok: (value: T) => U
 A function that will be called on the value contained if this is Ok.
Returns U
the return value of the Ok or Err matcher function
See
- unwrapOrElse
- unwrapOr
- Defined in result.ts:184

unwrapOr

unwrapOr(this: Result<T, E>, defaultValue: T): T
Returns the contained value if this is Ok, otherwise return the provided default value, ignoring any error value.
Parameters
- this: Result<T, E>
- defaultValue: T
 the value to return if this is Err
Returns T
the contained if this is Ok, otherwise defaultValue
See
- unwrapOrElse
- match
- Defined in result.ts:240

unwrapOrElse

unwrapOrElse(this: Result<T, E>, defaultValue: (error: E) => T): T
Returns the contained value if this is Ok, otherwise call the provided function with the error value and return the result.
Parameters
- this: Result<T, E>
- defaultValue: (error: E) => T
 a function that will be called on the error value if this is Err
Returns T
the contained if this is Ok, otherwise the return value from calling defaultValue on the error value
See
- unwrapOr
- match
- Defined in result.ts:223

Interacting with Option

err

err(this: Result<T, E>): Option<E>
If this is Err, returns Option.Some containing the value in this. Otherwise return Option.None.
Parameters
- this: Result<T, E>
Returns Option<E>
Option.Some with the value in this if this is Err, Option.None otherwise
See
- ok
- transpose
- Defined in result.ts:538

ok

ok(this: Result<T, E>): Option<T>
If this is Ok, returns Option.Some containing the value in this. Otherwise return Option.None.
Parameters
- this: Result<T, E>
Returns Option<T>
Option.Some with the value in this if this is Ok, Option.None otherwise
See
- err
- transpose
- Defined in result.ts:521

transpose

transpose<T extends {}>(this: Result<Option<T>, E>): Option<Result<T, E>>
Convert a Result containing an Option into an Option containing a Result.
Type Parameters
- T extends {}
 the type of the value contained in the Option contained in this
Parameters
- this: Result<Option<T>, E>
Returns Option<Result<T, E>>
if this is Err, returns Option.Some containing this; if this is Ok and the Option in this is Option.None, returns Option.None; otherwise returns Option.Some containing Ok containing the value in the Option in this
See
- ok
- err
- Defined in result.ts:559

Querying the variant

isErr

isErr(this: Result<T, E>): boolean
Check if this is Err.
Parameters
- this: Result<T, E>
Returns boolean
true if this is Err, false otherwise

See
isOk
- Defined in result.ts:169

isOk

isOk(this: Result<T, E>): boolean
Check if this is Ok.
Parameters
- this: Result<T, E>
Returns boolean
true if this is Ok, false otherwise

See
isErr
- Defined in result.ts:158

Transforming contained values

map

map(this: Result<T, E>, fn: (value: T) => U): Result<U, E>
Transforms Result<T, E> to Result<U, E> by applying the provided function to the contained value of Ok and leaving Err values unchanged.
Type Parameters
- U extends {}
 the type of the return value of fn
Parameters
- this: Result<T, E>
- fn: (value: T) => U
 the function to apply to the value contained if this is Ok
Returns Result<U, E>
this if this is Err, otherwise Ok containing the result of applying fn to the value in this
See
- mapAsync
- mapOr
- mapErr
- mapErrAsync
- collect
- Defined in result.ts:404

mapAsync

mapAsync(
this: Result<T, E>,
fn: (value: T) => Promise,
): Promise<Result<U, E>>
Transforms Result<T, E> to Promise<Result<U, E>> by applying the provided async function to the contained value of Ok and resolving Err values unchanged.
Type Parameters
- U extends {}
 the type of the value in the promise returned by fn
Parameters
- this: Result<T, E>
- fn: (value: T) => Promise
 the function to apply to the value contained if this is Ok
Returns Promise<Result<U, E>>
a promise resolving to this if this is Err, otherwise a promise resolving to Ok containing the value resolved by the promise returned from applying fn to the value in this
See
- map
- mapOr
- mapErr
- mapErrAsync
- collect
- Defined in result.ts:428

mapErr

mapErr<F extends {} = Error>(
this: Result<T, E>,
fn: (error: E) => F,
): Result<T, F>
Transforms Result<T, E> to Result<T, F> by applying the provided function to the contained value of Err and leaving Ok values unchanged.
Type Parameters
- F extends {} = Error
 the type of the return value of fn
Parameters
- this: Result<T, E>
- fn: (error: E) => F
 the function to apply to the value contained if this is Err
Returns Result<T, F>
this if this is Ok, otherwise Err containing the result of applying fn to the value in this
See
- map
- mapAsync
- mapOr
- mapErrAsync
- collect
- Defined in result.ts:474

mapErrAsync

mapErrAsync<F extends {} = Error>(
this: Result<T, E>,
fn: (error: E) => Promise<F>,
): Promise<Result<T, F>>
Transforms Result<T, E> to Promise<Result<T, F>> by applying the provided async function to the contained value of Err and resolving Ok values unchanged.
Type Parameters
- F extends {} = Error
 the type of the value in the promise returned by fn
Parameters
- this: Result<T, E>
- fn: (error: E) => Promise<F>
 the function to apply to the value contained if this is Err
Returns Promise<Result<T, F>>
a promise resolving to this if this is Ok, otherwise a promise resolving to Err containing the value resolved by the promise returned from applying fn to the value in this
See
- map
- mapAsync
- mapOr
- mapErr
- collect
- Defined in result.ts:501

mapOr

mapOr(this: Result<T, E>, defaultValue: U, fn: (value: T) => U): U
Applies the provided function to the contained value if this is Ok, otherwise returns the provided default value.
Type Parameters
- U extends {}
 the type of defaultValue and the value returned by fn
Parameters
- this: Result<T, E>
- defaultValue: U
 the value to return if this is Err
- fn: (value: T) => U
 the function to apply to the value contained if this is Ok
Returns U
the result of applying fn to the value in this if this is Ok, otherwise defaultValue
See
- map
- mapAsync
- mapErr
- mapErrAsync
- collect
- Defined in result.ts:451

`Static`collect

collect<T extends {}, E extends {} = Error>(
results: Result<T, E>[],
): Result<T[], E>
Takes an Array of Result values. If any of the Result values in the array is Err, returns that Err. Otherwise, returns Ok containing an Array of each value inside each Result in the original list.
Type Parameters
- T extends {}
 the type contained by the Result values
- E extends {} = Error
 the error type of the Result values
Parameters
- results: Result<T, E>[]
 the Result values to collect
Returns Result<T[], E>
Ok containing an Array of values contained by each Result in the original Array if all Result values in the original list are Ok, otherwise returns the first Err in the Array
See
- map
- mapAsync
- mapOr
- mapErr
- mapErrAsync
- Defined in result.ts:85

Class Result<T, E>

Type Parameters

Index

Boolean operators

Constructing

Extracting the contained value

Interacting with Option

Querying the variant

Transforming contained values

Boolean operators

and

Type Parameters

Parameters

Returns Result<U, E>

See

andThen

Type Parameters

Parameters

Returns Result<U, E>

See

andThenAsync

Type Parameters

Parameters

Returns Promise<Result<U, E>>

See

or

Type Parameters

Parameters

Returns Result<T, F>

See

orElse

Type Parameters

Parameters

Returns Result<T, F>

See

orElseAsync

Type Parameters

Parameters

Returns Promise<Result<T, F>>

See

Constructing

StaticErr

Type Parameters

Parameters

Returns Result<T, E>

See

StaticOk

Type Parameters

Parameters

Returns Result<T, E>

See

Staticwrap

Type Parameters

Parameters

Returns Result<T, Option<{}>>

See

StaticwrapAsync

Type Parameters

Parameters

Returns Promise<Result<T, Option<{}>>>

See

Extracting the contained value

match

Type Parameters

Parameters

Err: (error: E) => U

Ok: (value: T) => U

Returns U

See

unwrapOr

Parameters

Returns T

See

unwrapOrElse

Parameters

Returns T

See

Interacting with Option

err

Parameters

`Static`Err

`Static`Ok

`Static`wrap

`Static`wrapAsync

`Static`collect