Category: JavaScript

Sometimes, we want to create rooms in Socket.io and JavaScript.

In this article, we’ll look at how to create rooms in Socket.io and JavaScript.

How to create rooms in Socket.io and JavaScript?

To create rooms in Socket.io and JavaScript, we just call join to join the room.

For instance, we write

io.sockets.on("connection", (socket) => {
  socket.on("create", (room) => {
    socket.join(room);
  });
});

to listen for the room create event on server side.

We get the room name and call join with it if the create event is emitted from client side.

On client side, we write

const socket = io.connect();
socket.emit("create", "room1");

to call socket.emit with 'create' and 'room1' to emit the create event with value 'room1‘.

Conclusion

To create rooms in Socket.io and JavaScript, we just call join to join the room.

Sometimes, we want to extract time from moment.js object with JavaScript.

In this article, we’ll look at how to extract time from moment.js object with JavaScript.

How to extract time from moment.js object with JavaScript?

To extract time from moment.js object with JavaScript, we can use the format method.

For instance, we write

const time = moment("2022-01-16T12:00:00").format("hh:mm:ss a");

to call format with "hh:mm:ss a" to return the time string of the date time in hours:minutes:seconds AM/PM format.

Conclusion

To extract time from moment.js object with JavaScript, we can use the format method.

Sometimes, we want to merge objects by id with JavaScript.

In this article, we’ll look at how to merge objects by id with JavaScript.

How to merge objects by id with JavaScript?

To merge objects by id with JavaScript, we use the map method and the spread operator.

For instance, we write

const a1 = [
  { id: 1, name: "test" },
  { id: 2, name: "test2" },
];
const a2 = [
  { id: 1, count: "1" },
  { id: 2, count: "2" },
];
const a3 = a1.map((t1) => ({ ...t1, ...a2.find((t2) => t2.id === t1.id) }));

to call a1.map with a callback that returns a new object with the properties of the object being looped through t1 spread into a new object.

And we get the object with the same id value as t1 with a2.find((t2) => t2.id === t1.id) and spread its properties into the same object.

The properties of the object that’s merged in the latest would override the property values of the items merged in earlier if they have the same property name.

Conclusion

To merge objects by id with JavaScript, we use the map method and the spread operator.

Sometimes, we want to get the length of a JavaScript associative array.

In this article, we’ll look at how to get the length of a JavaScript associative array.

How to get the length of a JavaScript associative array?

To get the length of a JavaScript associative array, we use the Object.keys method.

For instance, we write

const myObject = {};
myObject["q101"] = "Your name?";
myObject["q102"] = "Your age?";
myObject["q103"] = "Your school?";
console.log(Object.keys(myObject).length);

to define the myObject object.

Then we call Object.keys with myObject to return an array of non-inherited property key strings.

And then we get the length property of that to get the number of non-inherited properties in the object.

Conclusion

To get the length of a JavaScript associative array, we use the Object.keys method.

Sometimes, we want to convert milliseconds into date and time with Moment.js and JavaScript.

In this article, we’ll look at how to convert milliseconds into date and time with Moment.js and JavaScript.

How to convert milliseconds into date and time with Moment.js and JavaScript?

To convert milliseconds into date and time with Moment.js and JavaScript, we use the format method.

For instance, we write

const dateTime = moment(1454521239279).format("DD MMM YYYY hh:mm a");

to call moment with the millisecond timestamp.

Then we call format to convert the timestamp into a string with the human readable date and time.

Conclusion

To convert milliseconds into date and time with Moment.js and JavaScript, we use the format method.