cd src
npm install
tsc main.ts
node main.js

import * as Json from "./JsonDecoder";
type SomeDataType = {
    id: string,
    name: {
        firstname: string,
        lastname: string
    },
    hobbies: Array<string>,
    numbersAndStrings: Array<number|string>,
    optionalBoolean?: boolean
};
const decodeSomeDataType = Json.object<SomeDataType>({
    id: Json.string,
    name: Json.object({
        firstname: Json.string,
        lastname: Json.string
    }),
    hobbies: Json.array(Json.string),
    numbersAndStrings: Json.array(Json.oneOf<number|string>([Json.number, Json.string])),
    optionalBoolean: Json.maybe(undefined, Json.boolean)
});
console.log(decodeSomeDataType.run({
    id: "xy-12342",
    name: {
        firstname: "John",
        lastname: "Doe"
    },
    hobbies: [
        "Tennis",
        "Sleeping"
    ],
    numbersAndStrings: [
        1, 
        2,
        "foo",
        3,
        "bar"
    ]
}));

string : Decoder<string>
number : Decoder<number>
boolean : Decoder<boolean>
maybe: <a>(defaultValue: a, decoder: Decoder<a>): Decoder<a>
nullable: <a>(decoder: Decoder<a>): Decoder<null|a>
isnull: <a>(defaultValue:a): Decoder<a>
isundefined: <a>(defaultValue:a): Decoder<a>
isexactly: <a>(value:a): Decoder<a>
array: (decoder: Decoder<a>): Decoder<Array<a>>
keyValues: <a>(decoder: Decoder<a>): Decoder<{[name:string]: a}>
oneOf: (decoders: Array<Decoder<a>>): Decoder<a>
constant: <a>(value:a): Decoder<a>
lazy: <a>(mkDecoder: () => Decoder<a>): Decoder<a>
object: <a>(decoders: DecoderObject<a>): Decoder<a>
type DecoderObject<a> = {[t in keyof a]: Decoder<a[t]>}
decoder.map(f)
decoder.then(f)
decoder.run(json)
decoder.runThen(json, onOk, onErr)
decoder.runPromise(json) : Promise<a>