express-router.extension.js

const express = require("express");

module.exports = (app, { base = "" } = {}) => ({
    applyApi: api => app.use(base + api.base, buildRouter(api)),
    applyRoute: route => applyRoute(app, { base })(route),
    applyMiddleware: middleware => app.use(awaitHandlerFactory(middleware))
});

function buildRouter(api) {
    const routeReducer = (router, key) => applyRoute(router)(api.methods[key]);
    return Object.keys(api.methods).reduce(routeReducer, express.Router());
}

function applyRoute(app, { base = "" } = {}) {
    return route => {
        app[route.method.toLowerCase()](base + route.path, awaitHandlerFactory(route.handler));
        return app;
    };
}

function awaitHandlerFactory(middleware) {
    return async (req, res, next) => {
        try {
            await middleware(req, res, next);
        } catch (err) {
            next(err);
        }
    };
}