Category: JavaScript

Sometimes, we want to find index of an object by key and value in a JavaScript array.

In this article, we’ll look at how to find index of an object by key and value in a JavaScript array.

How to find index of an object by key and value in a JavaScript array?

To find index of an object by key and value in a JavaScript array, we can use the array findIndex method.

For instance, we write

const peoples = [
  { attr1: "bob", attr2: "pizza" },
  { attr1: "john", attr2: "sushi" },
  { attr1: "larry", attr2: "hummus" },
];

const index = peoples.findIndex((p) => p.attr1 == "john");

to call peoples.findIndex to find the index of the object in the peoples array with the attr1 property set to 'john'.

Conclusion

To find index of an object by key and value in a JavaScript array, we can use the array findIndex method.

Sometimes, we want to replace the last character of string using JavaScript.

In this article, we’ll look at how to replace the last character of string using JavaScript.

How to replace the last character of string using JavaScript?

To replace the last character of string using JavaScript, we can use the string replace method.

For instance, we write

const str1 = "Notion,Data,Identity,".replace(/.$/, ".");

to get the last character with the /.$/.

$ matches the end of a word.

And we replace it with a '.' with replace.

Conclusion

To replace the last character of string using JavaScript, we can use the string replace method.

Sometimes, we want to use JavaScript to limit a number between a min/max value.

In this article, we’ll look at how to use JavaScript to limit a number between a min/max value.

How to use JavaScript to limit a number between a min/max value?

To use JavaScript to limit a number between a min/max value, we can use the Math.min and Math.max methods.

For instance, we write

const limitNumberWithinRange = (num, min = 1, max = 20) => {
  const parsed = parseInt(num);
  return Math.min(Math.max(parsed, min), max);
};

to define the limitNumberWithinRange function.

In it, we parse num into an integer with parseInt.

Then we call Math.max with parsed and min to return the max between parsed and min.

Then we get the lower number from Math.max(parsed, min) and max with Math.min.

If parsed is less than min, then min is returned.

And if parsed is bigger than max, then max is returned.

Conclusion

To use JavaScript to limit a number between a min/max value, we can use the Math.min and Math.max methods.

Sometimes, we want to remove object properties with Lodash.

In this article, we’ll look at how to remove object properties with Lodash.

How to remove object properties with Lodash?

To remove object properties with Lodash, we can use the pick function.

For instance, we write

const model = {
  fName: null,
  lName: null,
};

const credentials = {
  fName: "xyz",
  lName: "abc",
  age: 23,
};

const result = _.pick(credentials, _.keys(model));

console.log(result);

to get the array of property keys from the model object with the keys function.

Then we call pick with credentials and the array of keys returned by the keys function to return a new object with the properties with the property names that are in the model object.

Conclusion

To remove object properties with Lodash, we can use the pick function.

Sometimes, we want to use socket.io in Express 4 and express-generator’s /bin/www.

In this article, we’ll look at how to use socket.io in Express 4 and express-generator’s /bin/www.

How to use socket.io in Express 4 and express-generator’s /bin/www?

To use socket.io in Express 4 and express-generator’s /bin/www, we can add the socket.io initialization code in its own file.

For instance, in socketApi.js, we write

const io = require("socket.io")();
const socketApi = {
  io,
};

io.on("connection", (socket) => {
  console.log("A user connected");
});

module.exports = socketApi;

to call io.on with 'connection' to listen for the connection event.

We export the socketApi with

module.exports = socketApi;

Then in /bin/www, we incorporate the socket.io code with

const app = require("../app");
const debug = require("debug")("socketexpress:server");
const http = require("http");
const socketApi = require("../socketApi");

const port = normalizePort(process.env.PORT || "3000");
app.set("port", port);

const server = http.createServer(app);
socketApi.io.attach(server);

//...

We call require to require the socketApi.js file.

Then we call socketApi.io.attach with the Express server to run the socket.io initialization code when we run our Express server.

Conclusion

To use socket.io in Express 4 and express-generator’s /bin/www, we can add the socket.io initialization code in its own file.