Prevent the execution of a post request function depending on the promise result?

Question

Prevent the execution of a post request function depending on the promise result?

When I handle a POST request in express, I am required to retrieve data from a mongoDB cluster and then respond accordingly based on the retrieved response.

app.post('/api/persons', (req, res) => {
  const data = req.body;

  if (!data.name || !data.number) {
    return res.status(400).json({
      error: 'Name or Number missing',
    });
  }

  const newName = data.name;
  
  Person.find({ name: newName }).then((result) => {
    if (result.length !== 0) {
      return res.status(409).json({
        error: 'Name must be unique',
      });
    }
  });

  const record = new Person({
    name: data.name,
    number: data.number,
  });

  record.save().then((savedRecord) => {
    res.json(savedRecord);
  });
});

Person represents a model in mongoDB

The Person.find method checks the value and returns a boolean. Currently, there are two issues that I need assistance with:

Even after returning a value in the function following the .find call, the process continues and the value gets saved using the record.save() below.
Despite the value being non-existent, the error message Name must be unique is displayed. // Solved it by replacing .exist() with .find()

Is there a way to resolve this without placing the record.save() inside the find promise? I prefer having the .find call within its own function. How can I achieve this?

Thank you

javascript express mongoose

Answer 1

Answer №1

To improve code organization, you can create a separate function called findPerson which will execute Person.find and accept newName, foundCallback, and notFoundCallback as parameters. Take a look at the following code snippet.

const findPerson = (newName, foundCallback, notFoundCallback) => {
    Person.find({ name: newName }).then((results) => {
        if (results.length !== 0) {
            foundCallback();
        } else {
            notFoundCallback();
        }
    });
}

app.post('/api/persons', (req, res) => {
    const data = req.body;

    if (!data.name || !data.number) {
        return res.status(400).json({
            error: 'Name or Number missing',
        });
    }

    const newName = data.name;

    findPerson(
        newName,
        () => res.status(409).json({ error: 'Name must be unique' }),
        () => {
            const newPerson = new Person({
                name: data.name,
                number: data.number,
            });

            newPerson.save().then((savedPerson) => {
                res.json(savedPerson);
            });
        }
    );
});

If you prefer using promises, you can refactor the solution as follows:

const checkUniquePerson = (newName) => {
    return new Promise((resolve, reject) => {
        Person.find({ name: newName }).then((results) => {
            if (results.length !== 0) {
                reject();
            } else {
                resolve();
            }
        });
    });
}

app.post('/api/persons', (req, res) => {
    const data = req.body;

    if (!data.name || !data.number) {
        return res.status(400).json({
            error: 'Name or Number missing',
        });
    }

    const newName = data.name;

    checkUniquePerson(newName).then(() => {
        const newPerson = new Person({
            name: data.name,
            number: data.number,
        });

        newPerson.save().then((savedPerson) => {
            res.json(savedPerson);
        });
    }).catch(() => {
        res.status(409).json({ error: 'Name must be unique' })
    });
});

Answer 2

To improve code organization, you can create a separate function called findPerson which will execute Person.find and accept newName, foundCallback, and notFoundCallback as parameters. Take a look at the following code snippet.

const findPerson = (newName, foundCallback, notFoundCallback) => {
    Person.find({ name: newName }).then((results) => {
        if (results.length !== 0) {
            foundCallback();
        } else {
            notFoundCallback();
        }
    });
}

app.post('/api/persons', (req, res) => {
    const data = req.body;

    if (!data.name || !data.number) {
        return res.status(400).json({
            error: 'Name or Number missing',
        });
    }

    const newName = data.name;

    findPerson(
        newName,
        () => res.status(409).json({ error: 'Name must be unique' }),
        () => {
            const newPerson = new Person({
                name: data.name,
                number: data.number,
            });

            newPerson.save().then((savedPerson) => {
                res.json(savedPerson);
            });
        }
    );
});

If you prefer using promises, you can refactor the solution as follows:

const checkUniquePerson = (newName) => {
    return new Promise((resolve, reject) => {
        Person.find({ name: newName }).then((results) => {
            if (results.length !== 0) {
                reject();
            } else {
                resolve();
            }
        });
    });
}

app.post('/api/persons', (req, res) => {
    const data = req.body;

    if (!data.name || !data.number) {
        return res.status(400).json({
            error: 'Name or Number missing',
        });
    }

    const newName = data.name;

    checkUniquePerson(newName).then(() => {
        const newPerson = new Person({
            name: data.name,
            number: data.number,
        });

        newPerson.save().then((savedPerson) => {
            res.json(savedPerson);
        });
    }).catch(() => {
        res.status(409).json({ error: 'Name must be unique' })
    });
});

Prevent the execution of a post request function depending on the promise result?

Answer №1

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