decoders

The decoders package provides useful utility decoder implementations.

import * as decoders from '@execonline-inc/decoders';

import Decoder, { fail, field, succeed } from 'jsonous';
import { fromEmpty, Maybe } from 'maybeasy';
import { Result } from 'resulty';

Functions

eql, stringLiteral

The eql decoder decodes for a specific value rather than some type. The stringLiteral decoder is an application of the eql decoder for just string values.

import { eql } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<123> = eql<123>(123);
const result: Result<string, 123> = example.decodeAny(123);

import { stringLiteral } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<'abc'> = stringLiteral('abc');
const result: Result<string, 'abc'> = example.decodeAny('abc');

regexDecoder

import { regexDecoder } from '@execonline-inc/decoders';
import Decoder, { fail, succeed } from 'jsonous';

const example: Decoder<string> = regexDecoder(/(abc)/).andThen(result =>
  fromEmpty(result[1]).map(str => succeed(str).getOrElse(() => fail('Could not find "abc"')))
);

nullableBlankString

This decoder handles a value that should be a string but could also be null or undefined and converts it to a Maybe.

import { nullableBlankString } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<Maybe<string>> = nullableBlankString;
const result: Result<string, Maybe<string>> = example.decodeAny('abc');

base64Decoder

This decoder decodes input as base64 using the browser's atob function. A decoder error is the result from any thrown errors.

import { base64Decoder } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<string> = base64Decoder;
const result: Result<string, string> = example.decodeAny('aGVsbG8=');

jsonParserDecoder

This decoder takes a decoder whose output is parsed as JSON. If JSON parsing fails, then a decoder error is the result.

import { base64Decoder, jsonParserDecoder } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<string> = jsonParserDecoder(base64Decoder);
const result: Result<string, string> = example.decodeAny('ImhlbGxvIg==');

pipeD

This decoder is used to run two decoders in sequence passing the successfully decoded value from the first as the input for the second.

import { base64Decoder, pipeD, stringLiteral } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<'hello'> = pipeD(base64Decoder, stringLiteral('hello'));
const result: Result<string, string> = example.decodeAny('aGVsbG8=');

numberToStringDecoder

import { numberToStringDecoder } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<string> = numberToStringDecoder;
const result: Result<string, string> = example.decodeAny(123);

stringToNumberDecoder

import { stringToNumberDecoder } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<number> = stringToNumberDecoder;
const result: Result<string, number> = example.decodeAny('123');

jsonValueDecoder

TODO

secondsDecoder

import { secondsDecoder } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const example: Decoder<Time> = secondsDecoder;
const result: Result<string, Time> = example.decodeAny(60);

explicitJust

This is used to decode a JSON object representing a Maybe monad that's expected to be a Just:

import { explicitJust } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const thing = { kind: 'just', value: 123 };
const example: Decoder<Maybe<number>> = explicitJust;
const result: Result<string, Maybe<number>> = example.decodeAny(thing);

explicitNothing

This is used to decode a JSON object representing a Maybe monad that's expected to be a Nothing:

import { explicitNothing } from '@execonline-inc/decoders';
import Decoder from 'jsonous';
import { Result } from 'resulty';

const thing = { kind: 'nothing' };
const example: Decoder<Maybe<number>> = explicitNothing;
const result: Result<string, Maybe<number>> = example.decodeAny(thing);

explicitMaybe

This is used to decode a JSON object representing a Maybe monad that could be either a Just or a Nothing.

mergeObjectDecoders

This will produce a single decoder by combining the decoded fields of the two given decoders.

If the given decoders overlap for any fields, the second decoder will decide the final value for those fields.

import { mergeObjectDecoders, stringLiteral } from '@execonline-inc/decoders';
import Decoder, { field } from 'jsonous';
import { Result } from 'resulty';

interface A {
  foo: string;
  bar: string;
}
interface B {
  bar: 'star';
  baz: 'jazz';
}

const objA: A = { foo: 'goo', bar: 'car' };
const objB: B = { bar: 'star', baz: 'jazz' };

const decoderA: Decoder<A> = succeed({})
  .assign('foo', field('foo', string))
  .assign('bar', field('bar', string));
const decoderB: Decoder<B> = succeed({})
  .assign('bar', field('bar', stringLiteral('star')))
  .assign('baz', field('baz', stringLiteral('jazz')));

const example: Decoder<A & B> = mergeObjectDecoders(decoderA, decoderB);
const result: Result<string, A & B> = example.decodeAny({ ...objA, ...objB });