andThen applied to decoders

andThen.js

import { field, string, boolean, number, succeed } from 'jsonous';

const decoder = 
  field('foo', string()).map(s => s + '-ish').andThen(foo =>
  field('bar', number()).map(n => n*2).andThen(bar =>
  field('baz', boolean()).map(b => !b).andThen(baz =>
  succeed({ foo, bar, baz }))));

decoder.decodeAny({ foo: 'hello', bar: 42, baz: true }); 
// --> Ok({ foo: 'hello-ish', bar: 84, baz: false })

decoder.decodeAny({ foo: 'hello', bar: 'fourty-two', baz: true });
// --> Err('Error found in field 'bar' of {"foo":"hello","bar":"fourty-two","baz":true}: Expected to find a number. Instead found "fourty-two"');