解碼日期

如果你有一個像這樣的 ISO 日期字串的 json

JSON.stringify({date: new Date()})
// -> "{"date":"2016-12-12T13:24:34.470Z"}"

你可以把它對映到 elm Date 型別：

import Html exposing (text)
import Json.Decode as JD
import Date

payload = """{"date":"2016-12-12T13:24:34.470Z"}"""

dateDecoder : JD.Decoder Date.Date
dateDecoder =
  JD.string
    |> JD.andThen ( \str ->
          case Date.fromString str of
            Err err -> JD.fail err
            Ok date -> JD.succeed date )

payloadDecoder : JD.Decoder Date.Date
payloadDecoder =
  JD.field "date" dateDecoder

main =
  JD.decodeString payloadDecoder payload
  |> toString
  |> text