Class Err<T>

constructor

• new Err<T>(issues: readonly DecodingIssue[]): Err<T>

  Creates a new Err instance from structured decoding issues.

  Type Parameters

  • T

    The type that would have been returned if successful

  Parameters

  • issues: readonly DecodingIssue[]

    The list of issues describing what went wrong and where.

  Returns Err<T>

Readonlyissues

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([{ message: "Invalid input", path: [] }]);
  if (!result.isOk()) {
    // TypeScript knows result.issues exists here
    console.log(result.issues);
  }
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map

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

  Returns a new Err with the same issues 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 issues

  Example

  const result: Result<number> = err("Invalid input");
  const mapped: Result<string> = result.map(x => x.toString());
  // mapped = Err([{ message: "Invalid input", path: [] }])
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