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    Function safeParseInt

    • Safely parses a base-10 integer from a string, returning a Result that is Ok<Int> for valid input and Err<Error> otherwise.

      This is a stricter alternative to both parseInt and Number:

      • Unlike parseInt('12abc', 10) (which returns 12), trailing non-numeric characters make the whole input invalid and yield Err.
      • Unlike Number('') / Number(' ') (which return 0), empty or whitespace-only input yields Err.

      The empty-string case is rejected by delegating to parseInt (which returns NaN there) rather than hard-coding a check, while the trailing- garbage case is rejected via Number. Valid input is truncated toward zero, so '12.9' becomes 12 and '-3.5' becomes -3.

      Only base 10 is supported. Use Result.unwrapOk (optionally with a ?? Number.NaN fallback) or Result.unwrapOkOr to get a plain number back.

      Parameters

      • s: string

        The string to parse.

      Returns Result<Int, Error>

      Result.ok(parsedInt) for valid input, otherwise Result.err wrapping an Error describing the invalid input.

      assert.strictEqual(
        Result.unwrapOkOr(Num.safeParseInt('123'), Number.NaN),
        123,
      );

      assert.strictEqual(
        Result.unwrapOkOr(Num.safeParseInt('12.9'), Number.NaN),
        12,
      );

      assert.strictEqual(
        Result.unwrapOkOr(Num.safeParseInt('-12.9'), Number.NaN),
        -12,
      );

      assert.strictEqual(Number.parseInt('-12.9', 10), -12);

      // Native `parseInt` ignores trailing non-numeric characters

      assert.strictEqual(Number.parseInt('123abc', 10), 123);

      assert.isTrue(Number.isNaN(Number('123abc')));

      assert.isTrue(Result.isErr(Num.safeParseInt('123abc')));

      // Whitespace is not a valid integer, so we return an error instead of coercing to 0.

      assert.isTrue(Number.isNaN(Number.parseInt('  ', 10)));

      assert.strictEqual(Number('  '), 0); // Native `Number` coerces whitespace to 0

      assert.isTrue(Result.isErr(Num.safeParseInt('')));

      assert.strictEqual(Result.unwrapOk(Num.safeParseInt('  ')), undefined);

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