Class Decoder<T>Abstract

Abstract name

Abstract decode

• decode(arg): DecodingResult<T>

• Decodes a value and either succeeds with the decoded value or fails with a reason.

  Parameters

  • arg: unknown

    value to decode

  Returns DecodingResult<T>

map

• map<U>(tranformer): Decoder<U>

• An alias for transform.

  Type Parameters

  • U

  Parameters

  • tranformer: ((decoded) => U)

    transformer function

    • • (decoded): U

      • Parameters

        • decoded: T

        Returns U

  Returns Decoder<U>

  a decoder of the transformed value

or

• or<U>(other): Decoder<T | U>

• Takes a decoder of U and produces a decoder of the union of T | U.

  Useful for composing decoders that can decode many types.

  Example:

  asString.or(asNumber) // produces a decoder for string | number
  asString.or(asNumber).or(asBoolean)) // produces a decoder for string | number | boolean
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  Type Parameters

  • U

  Parameters

  • other: Decoder<U>

    decoder for next type U

  Returns Decoder<T | U>

  A decoder for decoding T | U

parse

• parse(arg): T

• Similar to decode, but throws an error if decoding fails.

  Parameters

  • arg: unknown

    value to decode

  Returns T

  decoded value

Abstract test

• test(arg): boolean

• Tests if a value can be decoded by this decoder.

  Parameters

  • arg: unknown

    value to test

  Returns boolean

transform

• transform<U>(transformer): Decoder<U>

• Makes it possible to apply some transformation on a decoded value.

  const asInt = asNumber.transform(num => parseInt(num))
  asInt.parse(117.565) // produces 117
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  Type Parameters

  • U

  Parameters

  • transformer: ((decoded) => U)

    transformer function

    • • (decoded): U

      • Parameters

        • decoded: T

        Returns U

  Returns Decoder<U>

  a decoder of the transformed value

try

• try<U>(operation): Decoder<U>

• Applies an operation that can also fail to this decoder.

  const asInt = asNumber.try(num => {
       if (Number.isInteger(number))  return success(num)
       else return failure("expected integer but got " + num)
  })
  asInt.parse(117.565) // throws error - $root: expected integer but got 117.565
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  Type Parameters

  • U

  Parameters

  • operation: ((decoded) => DecodingResult<U>)

    operation to apply post decoding

    • • (decoded): DecodingResult<U>

      • Parameters

        • decoded: T

        Returns DecodingResult<U>

  Returns Decoder<U>

  a decoder