A helper function for promise returning express middleware

respond.js

// Assumes:
// 1. application/json response content type
// 2. registered error handler capable of handling rejections
module.exports = function respond(handler) {
    return async (req, res, next) => {
        try {
            const result = await handler(req);
            res.json(result);
        }
        catch(err) {
            next(err);
        }
    };
};

Use in express routes like:

.post('/', respond(async req => {
    //... async/await workflow here
}));

Can be used with simple Promise returning middleware without async:

.post('/', respond(req => Model.save(req.body)));