Class Err<T>

constructor

• new Err<T>(error: string): Err<T>

  Creates a new Err instance containing an error message.

  Type Parameters

  • T

  Parameters

  • error: string

    The error message describing what went wrong

  Returns Err<T>

Readonlyerror

isOk

• isOk(): this is Ok<T>

  Type guard to check if this Result is an Ok. Always returns false for Err instances.

  Returns this is Ok<T>

  false for Err instances

  Example

  const result: Result<number> = err("Invalid input");
  if (!result.isOk()) {
    // TypeScript knows result.error exists here
    console.log(result.error);
  }
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map

• map<O>(_fn: (value: T) => O): Result<O>

  Returns a new Err with the same error message but a different type parameter. Since this represents an error, the transform function is never called.

  Type Parameters

  • O

    The new type parameter

  Parameters

  • _fn: (value: T) => O

    The function that would have transformed the value (ignored)

  Returns Result<O>

  A new Err with the same error message

  Example

  const result: Result<number> = err("Invalid input");
  const mapped: Result<string> = result.map(x => x.toString());
  // mapped = Err("Invalid input")
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