Interface Result<T, E>

type

andThen

• andThen<U>(fn): Result<U, E>

• Transforms the Result by applying a function that returns a Result to the contained Ok value, chaining multiple potentially failing operations.

  Type Parameters

  • U extends NonUndefined

  Parameters

  • fn: ((val) => Result<U, E>)

    A function that takes the current Result's Ok value and returns a new Result.

    • • (val): Result<U, E>

      • Parameters

        • val: T

        Returns Result<U, E>

  Returns Result<U, E>

  The Result returned by the function if the original Result is Ok, otherwise the original Err.

  Examples

  const parse = (s: string) => {
    const parsed = parseInt(s);
    return isNaN(parsed) ? Err("NaN") : Ok(parsed);
  };
  const result = Ok("123").andThen(parse); // Ok(123)
  const noResult = Err("NaN").andThen(parse); // Err("NaN")
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err

• err(): Option<E>

• Converts the Result to an Option containing the error value, or None if Ok.

  Returns Option<E>

  An Option of the error value if Err, otherwise None.

  Examples

  const result = Ok(5).err(); // None
  const error = Err("error").err(); // Some("error")
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isErr

• isErr(): this is ErrResult<T, E>

• Checks if the Result is an Err.

  Returns this is ErrResult<T, E>

  true if the Result is Err, otherwise false.

  Example

  console.log(Ok(5).isErr()); // false
  console.log(Err("error").isErr()); // true
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isOk

• isOk(): this is OkResult<T, E>

• Checks if the Result is an Ok.

  Returns this is OkResult<T, E>

  true if the Result is Ok, otherwise false.

  Example

  console.log(Ok(5).isOk()); // true
  console.log(Err("error").isOk()); // false
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map

• map<U>(fn): Result<U, E>

• Maps a Result<Ok, Err> to Result<U, Err> by applying a function to a contained Ok value, leaving an Err value untouched.

  Type Parameters

  • U extends NonUndefined

  Parameters

  • fn: ((val) => U)

    A function to apply to the contained Ok value.

    • • (val): U

      • Parameters

        • val: T

        Returns U

  Returns Result<U, E>

  A Result containing the transformed value if Ok, or the original Err.

  Examples

  const length = Ok("hello").map(s => s.length); // Ok(5)
  const error = Err("error").map(s => s.length); // Err("error")
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mapErr

• mapErr<F>(fn): Result<T, F>

• Maps a Result<Ok, Err> to Result<Ok, F> by applying a function to a contained Err value, leaving an Ok value untouched.

  Type Parameters

  • F extends NonUndefined

  Parameters

  • fn: ((err) => F)

    A function to apply to the contained Err value.

    • • (err): F

      • Parameters

        • err: E

        Returns F

  Returns Result<T, F>

  A Result containing the original Ok, or the transformed Err.

  Examples

  const ok = Ok("hello").mapErr(err => `Error: ${err}`); // Ok("hello")
  const error = Err("error").mapErr(err => `Error: ${err}`); // Err("Error: error")
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match

• match<U>(fn): U

• Performs a match operation on the Result, allowing for branching logic based on its state.

  Type Parameters

  • U extends NonUndefined

  Parameters

  • fn: Match<T, E, U>

    An object with functions to handle each case: Ok or Err.

  Returns U

  The result of applying the appropriate function based on the Result's state.

  Examples

  const result = Ok(5).match({
    ok: (val) => `Success: ${val}`,
    err: (val) => `Error: ${val}`,
  });
  // result === "Success: 5"
  
  const error = Err("failure").match({
    ok: (val) => `Success: ${val}`,
    err: (val) => `Error: ${val}`,
  });
  // error === "Error: failure"
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ok

• ok(): Option<T>

• Converts the Result to an Option containing the success value, or None if Err.

  Returns Option<T>

  An Option of the success value if Ok, otherwise None.

  Examples

  const result = Ok(5).ok(); // Some(5)
  const error = Err("error").ok(); // None
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orElse

• orElse<F>(fn): Result<T, F>

• Applies a function to the contained Err value if present, or returns the Ok value if present.

  Type Parameters

  • F extends NonUndefined

  Parameters

  • fn: ((err) => Result<T, F>)

    A function that takes the current Result's Err value and returns a new Result.

    • • (err): Result<T, F>

      • Parameters

        • err: E

        Returns Result<T, F>

  Returns Result<T, F>

  The original Ok if present, or the Result of the function applied to the Err value.

  Examples

  const ok = Ok("hello").orElse(err => Err(`Error: ${err}`)); // Ok("hello")
  const error = Err("error").orElse(err => Ok(`Recovered from ${err}`)); // Ok("Recovered from error")
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unwrap

• unwrap(): T

• Unwraps a Result, yielding the contained success value if Ok, otherwise throws an error.

  Returns T

  The contained success value.

  Throws

  Error if the Result is Err.

  Examples

  console.log(Ok("value").unwrap()); // "value"
  console.log(Err("error").unwrap()); // throws Error
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unwrapErr

• unwrapErr(): E

• Unwraps a Result, yielding the contained error value if Err, otherwise throws an error.

  Returns E

  The contained error value.

  Throws

  Error if the Result is Ok.

  Examples

  console.log(Err("error").unwrapErr()); // "error"
  console.log(Ok("value").unwrapErr()); // throws Error
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unwrapOr

• unwrapOr(def): T

• Returns the contained success value if Ok, otherwise returns the provided default value.

  Parameters

  • def: T

    The default value to return if the Result is Err.

  Returns T

  The contained success value if Ok, otherwise def.

  Examples

  const result = Ok("value").unwrapOr("default"); // "value"
  const error = Err("error").unwrapOr("default"); // "default"
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