Category: JavaScript

Sometimes, we want to pass variables to the next middleware using next() in Express.js.

In this article, we’ll look at how to pass variables to the next middleware using next() in Express.js.

How to pass variables to the next middleware using next() in Express.js?

To pass variables to the next middleware using next() in Express.js, we can add the data to the res object.

For instance, we write

app.use((req, res, next) => {
  res.locals.user = req.user;
  res.locals.authenticated = !req.user.anonymous;
  next();
});

app.use((req, res, next) => {
  if (res.locals.authenticated) {
    console.log(res.locals.user.id);
  }
  next();
});

to set res.locals to some values in the first middleware.

And then we call next to call the next middleware function.

Then in the 2nd middleware, we check the values that we set as properties of res.

Conclusion

To pass variables to the next middleware using next() in Express.js, we can add the data to the res object.

Sometimes, we want to find home directory in platform agnostic way with Node.js.

In this article, we’ll look at how to find home directory in platform agnostic way with Node.js.

How to find home directory in platform agnostic way with Node.js?

To find home directory in platform agnostic way with Node.js, we can use the os.homedir method.

For instance, we write

const os = require('os');

console.log(os.homedir());

to call os.homedir to return the home directory path as a string.

Conclusion

To find home directory in platform agnostic way with Node.js, we can use the os.homedir method.

Sometimes, we want to generate unique ID with Node.js.

In this article, we’ll look at how to generate unique ID with Node.js.

How to generate unique ID with Node.js?

To generate unique ID with Node.js, we can use the uuid package.

For instance, we run

npm install uuid

Then we use it by writing

const {
  v1: uuidv1,
  v4: uuidv4,
} = require('uuid');

uuidv1();
uuidv4()

to call uuidv1 to return v1 UUID strings and call uuidv4 to return v4 UUID strings.

Conclusion

To generate unique ID with Node.js, we can use the uuid package.

Sometimes, we want to search an array of objects in MongoDB.

In this article, we’ll look at how to search an array of objects in MongoDB.

How to search an array of objects in MongoDB?

To search an array of objects in MongoDB, we can use the $elemMatch operator.

For instance, we write

db.users.find({
  awards: {
    $elemMatch: {
      award: 'Medal',
      year: 1975
    }
  }
})

to search the awards array in the users collection for users with an awards entry that has the award property set to 'Medal' and year set to 1975.

Conclusion

To search an array of objects in MongoDB, we can use the $elemMatch operator.

Sometimes, we want to push items into Mongo array via Mongoose.

In this article, we’ll look at how to push items into Mongo array via Mongoose.

How to push items into Mongo array via Mongoose?

To push items into Mongo array via Mongoose, we can use the array push method.

For instance, we write

person.friends.push(friend);
person.save(done);

to call push on person.friends to append a new entry to the person‘s friends collection.

And then we call person.save to save the person entry.

Conclusion

To push items into Mongo array via Mongoose, we can use the array push method.