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Node/Express return error to main function?

I'm in a situation where I have a POST route that calls a function multiple times. I want the request to return an error if the called function returns an error, but I am not sure how to achieve this. See this image:

This is my code:

function POSTcord(lat, lng) {
    axios
    .post(process.env.SOS_POST_URL + process.env.SOS_POST_CODE, {
        batteryLevel: 100,
        longitude: lng,
        latitude: lat
    })
    .then(res => {
        console.log(`statusCode: ${res.status}`)
    })
    .catch(error => {
        console.error(error.message);
    })
}

router.post('/test', async (req, res) => {
    let passedCords = req.body;
    try {
        for (const cord of passedCords) {
            POSTcord(cord.lat, cord.lng);
        }
        res.status(200).json({status:"success", message: "hello!"});
      } catch (err) {
        console.error(err.message);
        res.status(500).send("Server error");
      }
});

I want the route /test to return an error if the function POSTcord catches an error somewhere in the loop. Any ideas on this? I'm thinking I could pass res to POSTcord function, but that didn't work. Thankful for any input :)

about 4 years ago · Juan Pablo Isaza

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Accepted Answer · 2022-07-10T12:59:56.054Z

You need to return the Promise and make sure the error is thrown/rejected:

Either do this:

function POSTcord(lat, lng) {
    return axios // <--------------- THIS IS VERY IMPORTANT
    .post(process.env.SOS_POST_URL + process.env.SOS_POST_CODE, {
        batteryLevel: 100,
        longitude: lng,
        latitude: lat
    })
    .then(res => {
        console.log(`statusCode: ${res.status}`)
    })
    .catch(error => {
        console.error(error.message);
        throw error; // <----------- ALSO DO THIS
    })
}

Or do this:

function POSTcord(lat, lng) {
    return axios // <--------------- THIS IS VERY IMPORTANT
    .post(process.env.SOS_POST_URL + process.env.SOS_POST_CODE, {
        batteryLevel: 100,
        longitude: lng,
        latitude: lat
    })
    .then(res => {
        console.log(`statusCode: ${res.status}`)
    })
    // DON'T CATCH THE ERROR!!
}

Then all you need to do is await to get the error:

router.post('/test', async (req, res) => {
    let passedCords = req.body;
    try {
        for (const cord of passedCords) {
            await POSTcord(cord.lat, cord.lng); // DO THIS FOR CATCH TO WORK
        }
        res.status(200).json({status:"success", message: "hello!"});
      } catch (err) {
        console.error(err.message);
        res.status(500).send("Server error");
      }
});

If you want to call POSTcord() in parallel you can await using Promise.all():

router.post('/test', async (req, res) => {
    let passedCords = req.body;
    try {
        let promises = [];
        for (const cord of passedCords) {
            let p = POSTcord(cord.lat, cord.lng);
            promises.push(p);
        }

        await Promise.all(promises); // DO THIS FOR CATCH TO WORK

        res.status(200).json({status:"success", message: "hello!"});
      } catch (err) {
        console.error(err.message);
        res.status(500).send("Server error");
      }
});

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Node/Express return error to main function?

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