Stateful domain thing for maintaining context across async calls

domain.js

'use strict';

const Domain = require('domain');

const create = function (initialState = {}) {
    const domain = Domain.create();
  
    domain.state = initialState;

    const enter = domain.enter;
    const exit = domain.exit;

    domain.enter = function () {
        const state = process.domain ? process.domain.state : undefined;

        if (process.domain) {
            domain.parent = process.domain;
            domain.state = Object.assign(domain.state, process.domain.state);
        }

        enter.call(domain);
    };

    domain.exit = function () {
        const state = domain.state;

        if (domain.parent) {
            domain.parent = undefined;
        }

        exit.call(domain);

        if (process.domain) {
            process.domain.state = Object.assign(process.domain.state || {}, state);
        }
    }

    return domain;
};

module.exports = { create, get state() { return process.domain && process.domain.state } };