result-type-ts

A TypeScript library for the Result<T, E> type, which is supported in modern languages like Rust, Swift, Kotlin.

Features

• 0 dependencies
• Provides many sophisticated functions, properties, and methods
• Well-tested
• Works on both browsers and Node.js
• Strict type inference

API

Functions

Example

const result = Result.success(123)
console.log(result.value) // 123

Example

const result = Result.failure('error')
console.log(result.error) // error

Example

const result = Result.tryCatch(() => 123)
console.log(result.value) // 123

const result2 = Result.tryCatch(() => {
  throw 'error'
})
console.log(result2.error) // error

Example

const result = Result.fromNullish(123);
console.log(result.value) // 123

const result2 = Result.fromNullish(null);
console.log(result2.error) // null
console.log(result2.isFailure) // true

Example

const result = await Result.fromPromise(Promise.resolve(123))
console.log(result.value) // 123

const result2 = await Result.fromPromise(Promise.reject('error'))
console.log(result2.error) // error

Example

const result = await Result.all([Result.success(123), Result.success(456)])
console.log(result.value) // 123

const result2 = await Result.all([Result.success(123), Result.failure('error')])
console.log(result2.error) // error

const result3 = await Result.all([Result.failure('error'), Result.failure('error2')])
console.log(result3.error) // error

Types

Example

const result: Result.Success<number> = Result.success(123)

Example

const result: Result.Failure<string> = Result.failure('error')

Example

const result: Result<number, string> = Math.random() > 0.5 ? Result.success(123) : Result.failure('error')

Properties

Example

const result = Result.success(123)
console.log(result.value) // 123

const result2 = Result.failure('error')
console.log(result2.value) // undefined

Example

const result = Result.success(123)
console.log(result.error) // undefined

const result2 = Result.failure('error')
console.log(result2.error) // error

Example

const result = Result.success(123)
console.log(result.isSuccess) // true

const result2 = Result.failure('error')
console.log(result2.isSuccess) // false

Example

const result = Result.success(123)
console.log(result.isFailure) // false

const result2 = Result.failure('error')
console.log(result2.isFailure) // true

Methods

Example

const result = Result.success(123)
console.log(result.getOrThrow()) // 123

const result2 = Result.failure('error')
try {
  result2.getOrThrow()
} catch (e) {
  console.log(e) // error
}

Example

const result = Result.success(123)
console.log(result.toUnion()) // 123

const result2 = Result.failure('error')
console.log(result2.toUnion()) // error

Example

const result = Result.success(123)
console.log(result.ifSuccess((value) => value * 2)) // 246

const result2 = Result.failure('error')
console.log(result2.ifSuccess((value) => value * 2)) // undefined

Example

const result = Result.success(123)
console.log(result.ifFailure((error) => error + '!')) // undefined

const result2 = Result.failure('error')
console.log(result2.ifFailure((error) => error + '!')) // error!

Example

const result = Result.success(123)
console.log(result.match((value) => value * 2, (error) => error + '!')) // 246

const result2 = Result.failure('error')
console.log(result2.match((value) => value * 2, (error) => error + '!')) // error!

Example

const result = Result.success(123).map((value) => value * 2)
console.log(result.value) // 246

const result2 = Result.failure('error').map((value) => value * 2)
console.log(result2.error) // error

Example

const result = Result.success(123).mapError((error) => error + '!')
console.log(result.value) // 123

const result2 = Result.failure('error').mapError((error) => error + '!')
console.log(result2.error) // error!

Example

const result = Result.success(123).flatMap((value) => Result.success(value * 2))
console.log(result.value) // 246

const result2 = Result.failure('error').flatMap((value) => Result.failure(value * 2))
console.log(result2.error) // error

Example

const result = Result.success(Result.success(123)).flatten()
console.log(result.value) // 246

const result2 = Result.success(Result.failure('error')).flatten()
console.log(result2.error) // error

const result3 = Result.failure('error').flatten()
console.log(result3.error) // error

Example

const result: Result<number, Error> = Result.tryCatch(() => {
  if (Math.random() >= 0) {
    throw new Error('error')
  } else {
    return 123
  }
}).assertErrorInstanceOf(Error)
console.log(result.isFailure && result.error.message) // error