Don't work function with promise

Question

I try this code:

function addNewCars(req, res) {
    let CarsList = req.body;
    carListParsing(carList)
        .then(function () {
        console.log('OK');
        res.status(200).send('OK');
    }).catch(function (err) {
        res.status(200).send(err);
    });
}

function carListParsing (data) {
    return new Promise(function (resolve, reject) {

        let newCar = {};
        newCar.name = data.car_name;
        validateCar(newCar).then(function (data) {
            console.log('validate result1: ', data); //this line doesn't show 
            //if I get validation result, I can use next function createCat()
            resolve(data);
        }).catch(function (err) {
            reject(err);
        });
    });
}

function validateCar(data) {
    db.cars.findAll({where: {name: data.name}}).then(function (org) {
        if (org.length < 1) {
            console.log('validate1: OK'); //work
            return data;
        } else {
            console.log('validate2: already exist'); //work
            return new Error('The ' + data.name + ' car is already exist.');
        }
    }).catch(function (err) {
        return err;
    });
}

I neet to validate data => Car name, if car not exist then create new car and perform next logic, example park car. If car found, then perform function park car.

You forgot to return the promise from `validateCar`: `return db.cars....`. You should be seeing an error similar to "Cannot access property 'then' of 'undefined'". — Felix Kling, Jun 01 '17 at 04:07
I can't receive any errors. Idealy I would like to return only binary result Yes or No. In this case I return same data that I checked to continue work with them. Or return information that car is exist. — Sergei R, Jun 01 '17 at 05:13

score 2 · Accepted Answer · answered Jun 01 '17 at 05:36

Avoid the Promise constructor antipattern in carListParsing, and return your result promise from validateCar!

function addNewCars(req, res) {
    // CarsList is a typo
    carListParsing(req.body)
    .then(function () {
        console.log('OK');
        res.status(200).send('OK');
    }, function (err) { // more appropriate than catch
        res.status(200).send(err);
    });
}

function carListParsing (data) {
    let newCar = {
        name: data.car_name
    };
    // don't call `new Promise`
    return validateCar(newCar).then(function (data) {
       console.log('validate result1: ', data); //this line doesn't show 
       // if I get validation result, I can use next function createCat()
       return data; // don't resolve
    });
}

function validateCar(data) {
    return db.cars.findAll({where: {name: data.name}}).then(function (org) {
//  ^^^^^^
        if (org.length < 1) {
            console.log('validate1: OK'); //work
            return data;
        } else {
            console.log('validate2: already exist'); //work
            throw new Error('The ' + data.name + ' car is already exist.');
//          ^^^^^ probably what you actually wanted
        }
    }) // don't ignore errors
}

Don't work function with promise

1 Answers1