在 NodeJS (Express) 中使用 Promise.all 找不到集合时的 404 页面

Question

I use a Promise.all() and ask an URL in multiple Mongo collections.

I realized that some URLs are missing.

So I have a 404 page when it's the case. How to avoid that (typically, it's with the Annonce collection)? What can I replace Promise.all with?

const express = require('express');
const mongoose = require('mongoose');
const { ensureAuthenticated } = require('../helpers/auth');
const router = express.Router();

require('../models/Car');
const Car = mongoose.model('cars');

require('../models/Caratio');
const Caratio = mongoose.model('caratios');

require('../models/User');
const User = mongoose.model('users');

require('../models/Annonce');
const Annonce = mongoose.model('annonces');

router.get('/app/:cars_getroute', ensureAuthenticated, (req, res) => {
    Promise.all([Car.findOne({ cars_getroute: req.params.cars_getroute }),
                Caratio.findOne({ cars_getroute: req.params.cars_getroute }),
                Annonce.findOne({ cars_getroute: req.params.cars_getroute })])
        .then(result => {
            let [cars, caratios, annonces] = result;
}

Answer 1

Promise.all is all or nothing. It resolves once all promises in the array resolve, or reject as soon as one of them rejects. one alternative way is filtering your promises so that you only wait for resolved ones.

Promise.all([p1, p2, p3].map(toResultObject)).then((values) => {
    for (let i = 0; i < values.length; ++i) 
        if (!values[i].success) console.log("ERR: " + values[i].error);
        else console.log(values[i].result);
});

see Avoiding-Promise-all-fail-fast-behavior

NEW ANSWER

router.get('/app/:cars_getroute', ensureAuthenticated, async (req, res) => {
    const promises = [
        Car.findOne({
            cars_getroute: req.params.cars_getroute
        }),
        Caratio.findOne({
            cars_getroute: req.params.cars_getroute
        }),
        Annonce.findOne({
            cars_getroute: req.params.cars_getroute
        })
    ]

    let [cars, caratios, annonces] = await Promise.all(promises.map(p => p.catch(e => null)))
})

But of course you should check each value for nullability.

Answer 2

As Rafi said, as soon as a single promise fails in Promise.all , it will be rejected.

You can replace Promise.all with Promise.allSettled , so that a rejected promise will not impact (or stop) the other promises.

The Promise.allSettled() method returns a promise that resolves after all of the given promises have either resolved or rejected, with an array of objects that each describes the outcome of each promise.

Keep in mind that Promise.allSettled is fairly recent and is not supported by IE or Edge, and older versions of the other browsers.
Compatibility table