Category: JavaScript

Sometimes, we want to set max viewport in Puppeteer.

In this article, we’ll look at how to set max viewport in Puppeteer.

How to set max viewport in Puppeteer?

To set max viewport in Puppeteer, we set the defaultViewport option to null.

For instance, we write

const browser = await puppeteer.launch({ defaultViewport: null });

to call puppeteer.luanch with an object that has defaultViewport set to null.

This will make Puppeteer launch with the max viewport resolution instead of 800×600.

Conclusion

To set max viewport in Puppeteer, we set the defaultViewport option to null.

Sometimes, we want to parse XLSX and create JSON with Node.js.

In this article, we’ll look at how to parse XLSX and create JSON with Node.js.

How to parse XLSX and create JSON with Node.js?

To parse XLSX and create JSON with Node.js, we can use the xlsx package.

To install it, we run

npm i xlsx

Then we use it by writing

const XLSX = require("xlsx");
const workbook = XLSX.readFile("Master.xlsx");
const { SheetNames: sheetNames } = workbook;
console.log(XLSX.utils.sheet_to_json(workbook.Sheets[sheetNames[0]]));

to call XLSX.readFile to read the XLSX file from the path in the argument/

Then we get the sheetNames from the workbook object.

Next, we call XLSX.utils.sheet_to_json with the first sheet which we get from workbook.Sheets[sheetNames[0]] return the JSON data converted from the worksheet.

Conclusion

To parse XLSX and create JSON with Node.js, we can use the xlsx package.

Sometimes, we want to get a JSON via HTTP request in Node.js.

In this article, we’ll look at how to get a JSON via HTTP request in Node.js.

How to get a JSON via HTTP request in Node.js?

To get a JSON via HTTP request in Node.js, we can call request with json set to true.

For instance, we write

const options = {
  hostname: "127.0.0.1",
  port: app.get("port"),
  path: "/users",
  method: "GET",
  json: true,
};
request(options, (error, response, body) => {
  console.log(body);
});

to call request with json set to true in the options object to return a JSON response.

Then we get the parsed JSON response body from the body parameter in the callback.

Conclusion

To get a JSON via HTTP request in Node.js, we can call request with json set to true.

Sometimes, we want to scale socket.IO to multiple Node.js processes using cluster.

In this article, we’ll look at how to scale socket.IO to multiple Node.js processes using cluster.

How to scale socket.IO to multiple Node.js processes using cluster?

To scale socket.IO to multiple Node.js processes using cluster, we can use cluster to create workers processes.

For instance, we write

const cluster = require("cluster");
const os = require("os");

if (cluster.isMaster) {
  const server = require("http").createServer();
  const io = require("socket.io").listen(server);

  const RedisStore = require("socket.io/lib/stores/redis");
  const redis = require("socket.io/node_modules/redis");

  io.set(
    "store",
    new RedisStore({
      redisPub: redis.createClient(),
      redisSub: redis.createClient(),
      redisClient: redis.createClient(),
    })
  );

  setInterval(function () {
    io.sockets.emit("data", "payload");
  }, 1000);

  for (let i = 0; i < os.cpus().length; i++) {
    cluster.fork();
  }

  cluster.on("exit", (worker, code, signal) => {
    console.log("worker " + worker.process.pid + " died");
  });
}

if (cluster.isWorker) {
  const express = require("express");
  const app = express();

  const http = require("http");
  const server = http.createServer(app);
  const io = require("socket.io").listen(server);

  const RedisStore = require("socket.io/lib/stores/redis");
  const redis = require("socket.io/node_modules/redis");

  io.set(
    "store",
    new RedisStore({
      redisPub: redis.createClient(),
      redisSub: redis.createClient(),
      redisClient: redis.createClient(),
    })
  );

  io.sockets.on("connection", (socket) => {
    socket.emit("data", "connected to worker: " + cluster.worker.id);
  });

  app.listen(80);
}

to create a server on the master with

const server = require('http').createServer();

Then we call cluster.fork(); to create worker processes.

Then we create express servers on the workers with

const server = http.createServer(app);

We use Redis to do the caching with both the cluster master and worker.

Conclusion

To scale socket.IO to multiple Node.js processes using cluster, we can use cluster to create workers processes.

Sometimes, we want to download a file to disk from an AWS S3 bucket with Node.js.

In this article, we’ll look at how to download a file to disk from an AWS S3 bucket with Node.js.

How to download a file to disk from an AWS S3 bucket with Node.js?

To download a file to disk from an AWS S3 bucket with Node.js, we can create a read steam from the S3 client.

For instance, we write

const AWS = require("aws-sdk");
const path = require("path");
const fs = require("fs");

AWS.config.loadFromPath(path.resolve(__dirname, "config.json"));
AWS.config.update({
  accessKeyId: AWS.config.credentials.accessKeyId,
  secretAccessKey: AWS.config.credentials.secretAccessKey,
  region: AWS.config.region,
});

const s3 = new AWS.S3();
const params = {
  Bucket: "<your-bucket>",
  Key: "<path-to-your-file>",
};
const readStream = s3.getObject(params).createReadStream();
const writeStream = fs.createWriteStream(path.join(__dirname, "s3data.txt"));
readStream.pipe(writeStream);

to call s3.getObject to get the object from the bucket.

Then we call createReadStream from the returned object to read the file.

Next, we call fs.createWriteStream with the path to write to.

And then we call readStream.pipe with the writeStream to pipe the read stream data into the write stream to write the file to disk.

Conclusion

To download a file to disk from an AWS S3 bucket with Node.js, we can create a read steam from the S3 client.