Node js returning values from function

Question

I live in the PHP world but I am attempting to build out a REST Api using Node.

I have been stuck all day of trying to return an array of results from a for loop. Basically I am passing an array of field_name:field_value. I want to push the result from the update into an array to return. I can get it to log in the console but no further.

Here is a sample post json data

{
    "first_name":"Jeff",
    "phone":"4855555555"
}

Here is the function and loop

function UpdateKey(user_id, key, value, cb) {
    connection.query('UPDATE users SET ' + key + ' = ? WHERE id = ? LIMIT 1', [value, user_id], function(err, results) {
    if (err) {
        callback = key + " update failed.";
    } else {
        callback = key + " was updated.";
    }
    cb(callback);

  });
}    

for (myKey in post_data) {
  UpdateKey(user_id, myKey, post_data[myKey], function(id) {
    console.log(id);
  });
}

res.send(JSON.stringify({ "status": 200, "error": "", "response": my_results_here }));

I have been researching async but not sure the best route here. Any help would be great!

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — tkausl, Sep 30 '18 at 23:13
seem like You want to update fields in one query, but I see You're trying to unnecessarily loop through them — num8er, Sep 30 '18 at 23:22

score 1 · Accepted Answer · answered Sep 30 '18 at 23:17

1

You could collect all results in an array and send that when the arrays size equals the keys size:

const keys = Object.keys(post_data);
const response = [];

for(const myKey of keys) {
  UpdateKey(user_id, myKey, post_data[myKey], function(id) {
    response.push(id);
    if(keys.length === response.length) {
      res.send(JSON.stringify({ 
       status: 200, 
       error: "", 
       response
      }));
    }
  });
}

answered Sep 30 '18 at 23:17

Jonas Wilms

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Awesome, that works! Wish i asked this 8 hours ago! Thank you! – Tom Stokes Sep 30 '18 at 23:25

num8er · Answer 2 · 2018-09-30T23:46:28.523

The solution You want:

const updateUserField = (userId, field, value) => {
  return Promise((resolve) => {
    const query = 'UPDATE users SET ' + field + ' = ? WHERE id = ?';
    const data = [value, userId];
    connection.query(query, data, (error) => {
      if (error) return resolve(field + ' update failed');
      resolve(field + ' was updated');
    });
  });
};


router.post('/user/:id', async (req, res) => {
    const userId = req.params.id;
    const data = req.body;

    const response = [];
    for (const field in data) {
      response.push(
        await updateUserField(userId, field, data[field])
      );
    }

    res.status(200).send({
      response
    });
});

or in parallel:

router.post('/user/:id', async (req, res) => {
    const userId = req.params.id;
    const data = req.body;

    const response = await Promise.all(
      Object
        .keys(data)
        .map(field => updateUserField(userId, field, data[field]))
    );

    res.status(200).send({
      response
    });
});

Correct solution

As I understand You want to get post data and update record in users table.

So why not just do it in one query?

Try this way:

const updateUser = (userId, data) => {
  return Promise((resolve, reject) => {
    const query = 'UPDATE users SET ? WHERE id = ?';
    connection.query(query, [data, userId], (error) => {
      if (error) return reject(error);
      resolve();
    });
  });
};

router.post('/user/:id', async (req, res) => {
  try {
    const userId = req.params.id;
    const data = req.body;
    await updateUser(userId, data);
    res.status(200).send({
      message: 'User account successfully updated'
    })
  }
  catch (error) {
    console.error(error);
    res.status(500).send({
      message: 'Failed update user account'
    });
  }
});

But better think about using ORM i.e. Sequelize for security, validation and etc features that eases dev's life.

Node js returning values from function

2 Answers2