Pattern for handling errors in an efficient and streamlined manner

Question

Pattern for handling errors in an efficient and streamlined manner

Currently, I am exploring the use of Express for developing a basic JSON API. However, I have concerns about how to effectively manage input parameter validation and error handling in my project. Errors can occur during both the validation process and when accessing the database. Here's the current structure:

router.use(function(req, res, next) {
    validate(req.query).then(function() {
        next()
    }).catch(function(e) {
        next(e)
    })
})

router.get("/", function(req, res, next) {
    someDatabaseAccess(req.query).then(function(results) {
        res.json(results)
    }).catch(function(e) {
        next(e)
    })
})

router.use(function(e, req, res, next) {

    // ... (handling specific errors)

    res.status(400)
    res.json(someDummyResponse(e))
})

The validation process is defined as follows:

const validate = function(q) {
    return new Promise(function(resolve, reject) {
        if (q.someParameter) {
            if (somethingWrong(q.someParameter)) {
                reject(new Error("Something wrong!"))
            }
        }
        resolve()
    })
}

Do you think this approach is logical? Are there any suggestions on how I could improve or simplify it?

javascript express ecmascript-6 es6-promise

Answer 1

Answer №1

For validation purposes, I recommend using tools like JSONSchema. One of the options is to utilize a package such as tv4 for validation, although there are numerous similar tools available. Begin by creating a schema for the object:

const tv4 = require('tv4');

const schema = {
  type: object,
  properties: {
    name: string,
    phone: string
  },
  required: ['name']
};

In your route implementation, include the following:

app.post('/someroute', (req, res, next) => {
  if (!tv4.validate(req.body, schema)) 
    return next(new Error('not valid input'));
  // Perform necessary operations here
  res.end();
});

When it comes to error handling in Express, you can add a middleware function at the end with additional parameters:

// Add middleware
app.use(bodyParser.json())

// Add custom middleware
app.use(function(req, res, next) {
  // Implement necessary functionality
  next();
});    

// Define routes
app.get('/', () => {})

// Ensure that the error handler is always placed last
// Pay attention to the additional `err` parameter
app.use(function (err, req, res, next) {
  if (err) {
    // Log errors or handle exceptions accordingly
  }
  else next();
});

Answer 2

For validation purposes, I recommend using tools like JSONSchema. One of the options is to utilize a package such as tv4 for validation, although there are numerous similar tools available. Begin by creating a schema for the object:

const tv4 = require('tv4');

const schema = {
  type: object,
  properties: {
    name: string,
    phone: string
  },
  required: ['name']
};

In your route implementation, include the following:

app.post('/someroute', (req, res, next) => {
  if (!tv4.validate(req.body, schema)) 
    return next(new Error('not valid input'));
  // Perform necessary operations here
  res.end();
});

When it comes to error handling in Express, you can add a middleware function at the end with additional parameters:

// Add middleware
app.use(bodyParser.json())

// Add custom middleware
app.use(function(req, res, next) {
  // Implement necessary functionality
  next();
});    

// Define routes
app.get('/', () => {})

// Ensure that the error handler is always placed last
// Pay attention to the additional `err` parameter
app.use(function (err, req, res, next) {
  if (err) {
    // Log errors or handle exceptions accordingly
  }
  else next();
});

Answer 3

Answer №2

To enhance the organization of your application, consider creating a dedicated error configuration file and utilizing a middleware to handle errors. This approach will improve the overall structure of your app.

Error.json

"err":[
   "errorLog501":{
     "status":501,
     "message":"request is invalid"
    }
]

`

var errCodes = require('./error.json')
var errMiddleware = function(req, res, next) {
   if (req.body.hello) {
   // some cool stuff
     res.json(errCodes.errorLog501)
   } else {
     next();
   }
}

app.use(errMiddleware); //the middleware is invoked for every request made

It is crucial to include status codes in the JSON response for effective error handling on the frontend, ensuring users are informed about the application's current state.

Answer 4

To enhance the organization of your application, consider creating a dedicated error configuration file and utilizing a middleware to handle errors. This approach will improve the overall structure of your app.

Error.json

"err":[
   "errorLog501":{
     "status":501,
     "message":"request is invalid"
    }
]

`

var errCodes = require('./error.json')
var errMiddleware = function(req, res, next) {
   if (req.body.hello) {
   // some cool stuff
     res.json(errCodes.errorLog501)
   } else {
     next();
   }
}

app.use(errMiddleware); //the middleware is invoked for every request made

It is crucial to include status codes in the JSON response for effective error handling on the frontend, ensuring users are informed about the application's current state.

Pattern for handling errors in an efficient and streamlined manner

Answer №1

Answer №2

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