Author: John Au-Yeung

Sometimes, we want to update all clients using Socket.io.

In this article, we’ll look at how to update all clients using Socket.io.

How to update all clients using Socket.io?

To update all clients using Socket.io, we call socket.broadcast.emit to broadcast to all sockets except the socket that starts it.

For instance, we write

socket.broadcast.emit('users_count', clients);

to call socket.broadcast.emit with the event name and the value we want to send.

Conclusion

To update all clients using Socket.io, we call socket.broadcast.emit to broadcast to all sockets except the socket that starts it.

Sometimes, we want to write formatted JSON in Node.js.

In this article, we’ll look at how to write formatted JSON in Node.js.

How to write formatted JSON in Node.js?

To write formatted JSON in Node.js, we can call JSON.stringify with the 3rd argument set to the number of spaces to indent.

For instance, we write

JSON.stringify(object, null, 2)

to call JSON.stringify with the object to convert to a JSON string and 2 to indent each level of the JSON string to 2.

Conclusion

To write formatted JSON in Node.js, we can call JSON.stringify with the 3rd argument set to the number of spaces to indent.

Sometimes, we want to fix the req.user undefined error with Node.js, Express, and Passport.

In this article, we’ll look at how to fix the req.user undefined error with Node.js, Express, and Passport.

How to fix the req.user undefined error with Node.js, Express, and Passport?

To fix the req.user undefined error with Node.js, Express, and Passport, we should make sure Passport session state is set up in our app.

For instance, we should write

app.use(session({
  secret: 'anything'
}));
app.use(passport.initialize());
app.use(passport.session());

to call session to enable session storage with session.

Then we call passport.initialize to initialize Passport.

And then we call passport.session to let Passport handle sessions in our Express app.

Then when a user is logged in, req.user should be set.

Conclusion

To fix the req.user undefined error with Node.js, Express, and Passport, we should make sure Passport session state is set up in our app.

Sometimes, we want to create an empty file in Node.js.

In this article, we’ll look at how to create an empty file in Node.js.

How to create an empty file in Node.js?

To create an empty file in Node.js, we can call the fs.openSync method.

For instance, we write

fs.closeSync(fs.openSync(filePath, 'w'));

to call fs.openSync with the filePath of the file to write to and the 'w' (write) permission.

Then we close the returned file handle with fs.closeSync.

Conclusion

To create an empty file in Node.js, we can call the fs.openSync method.

Sometimes, we want to check if a variable exists with the Node.js Jade template engine.

In this article, we’ll look at how to check if a variable exists with the Node.js Jade template engine.

How to check if a variable exists with the Node.js Jade template engine?

To check if a variable exists with the Node.js Jade template engine, we can check if the property name with the variable name exists in the locals object.

For instance, we write

if locals.username
  p= username
else
  p No Username!

to check if the username template variable exists with if locals.username.

Conclusion

To check if a variable exists with the Node.js Jade template engine, we can check if the property name with the variable name exists in the locals object.