joplin-notes/joplin notion extension/Web Development/nodejs/Extras.md

Extras

• https://stackoverflow.com/questions/36022926/what-do-the-save-flags-do-with-npm-install npm i <package_name> --save and npm i <package_name> are same now and they also update dependencies of package too. to not update dependencies of package use npm i <package_name> --no-save

• nvm(Node version manager) curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash
 
nvm ls-remote : for getting list of available versions which can be downloaded
  nvm list : for getting list of downloaded versions of node
  nvm install 14.0.0 : for downloading and installing version 14.0.0
  nvm use 14.0.0 : switching to version 14.0.0
  nvm use system: switching to version when nodejs first installed nvm alias default 18.0: this will make 18 as default

• https://github.com/ishtms/learn-nodejs-hard-way (without installing other frameworks)

• https://youtu.be/Nh-252u80F4 : get wifi password

• Running nodejs in background https://sentrytwo.com/92df06609b

• To avoid running sudo Why You Should Never Run "sudo npm"... https://www.youtube.com/watch?v=aFrR56sqC_A

• pm2 PM2 is a production process manager for Node.js applications with a built-in load balancer. It allows you to keep applications alive forever, to reload them without downtime and to facilitate common system admin tasks. install this npm package globally or locally. npm i -g pm2 Using this we can start multiple node instances with single command. But first starting node application instances in background pm2 start app.js --name app1 same as node app.js but in background to stop node instance use pm2 stop app1 multiple node instance in file ecosystem.config.js

  module.exports = {
     apps: [
   	{
   	  name: 'main',
  
   	  script: 'index.js',
   	  watch: true,
   	  env: {
   		NODE_ENV: 'production',
   		PORT: 8081
   	  }
   	},
   	{
   	  name: 'ytdownloadspace',
   	  script: '../ytDownloadSpace/app.js',
   	  watch: true,
   	  env: {
   		NODE_ENV: 'production',
   		PORT: 8080
   	  }
   	},
   	{
   	  name: 'ytdlApi',
   	  script: '../ytdlApi/app.js',
   	  watch: true,
   	  env: {
   		NODE_ENV: 'production',
   		PORT: 8083
   	  }
   	}
     ]
  };
  
  

  and fiannly when use pm2 start ecosystem-config.js. To stop all these started with this file use pm2 stop ecosystem-config.js To list processes use pm2 list

• installing packages through repo link npm i https://github.com/expressjs/express https://www.pluralsight.com/resources/blog/guides/install-npm-packages-from-gitgithub  

• download a file with https and fs module

  const https = require("https"); // Use 'http' for non-HTTPS links
    const fs = require("fs");
  
    const fileUrl =
      "https://cdn.discordapp.com/attachments/1473231612341915668/1473231989501853819/packages_sorted2.txt?ex=699575b5&is=69942435&hm=66884969a27901525409ff1e5400619ea5305667a130476b7982e041c55297e8&"; // Replace with your file URL
    const destinationPath = "./downloaded-file.txt"; // Replace with desired local path and filename
  
    const file = fs.createWriteStream(destinationPath);
  
    https
      .get(fileUrl, (response) => {
        // Check if the request was successful (status code 200)
        if (response.statusCode !== 200) {
          console.error(`Download failed, status code: ${response.statusCode}`);
          file.close(); // Close the write stream
          fs.unlink(destinationPath, () => {}); // Delete the partial file
          return;
        }
  
        // Pipe the response stream to the file stream
        response.pipe(file);
  
        // Event listener for when the download is complete
        file.on("finish", () => {
          file.close();
          console.log("Download Completed!");
        });
      })
      .on("error", (err) => {
        // Handle network errors
        fs.unlink(destinationPath, () => {}); // Delete the partial file on error
        console.error("Error during download:", err.message);
      });
  
  

 

tips

1. to prevent adding of installed packages in package.json use --no-save flag when installing packages. eg: npm i --no-save sqlite3  

  better-sqlite guide https://www.w3resource.com/sqlite/snippets/better-sqlite3.php Comprehensive Guide to Better-SQLite3 (16_5_2026 5：48：16 am).html for parameterized query, string concatenation using ||

 selectQuery = `select * from ${songDataTableEnums.tablename}
     where ${songDataTableEnums.columns.songname} like  ? || '%' or ${songDataTableEnums.columns.songname} like  '% '|| ? || '%'
    or ${songDataTableEnums.columns.artist_name} like  ? || '%' or ${songDataTableEnums.columns.artist_name} like  '% '|| ? || '%'`;

 

generate thumbnails of video

const ffmpeg = require('fluent-ffmpeg');

ffmpeg('path/to/video.mp4')
  .screenshots({
    count: 1,
    timemarks: ['00:00:02'], // Capture at 2 seconds
    filename: 'thumbnail.png',
    folder: 'output/path/'
  });

or

ffmpeg('input.mp4')
  .screenshots({
    count: 3,                          // Number of screenshots to take
    timestamps: ['10%', '30sec', 60], // Locations: percentages, strings, or numbers (seconds)
    filename: 'thumbnail-at-%s-seconds.png', // %s inserts the timestamp
    folder: './output',                // Destination directory
    size: '320x240'                    // Rescales output width x height
  })
  .on('end', () => {
    console.log('Screenshots taken successfully!');
  })
  .on('error', (err) => {
    console.error('An error occurred: ' + err.message);
  });

• count: Total number of images to generate. If timestamps is not provided, it automatically distributes screenshots evenly across the video duration.
• timestamps: An array specifying exact positions to snapshot.
• Numbers represent absolute seconds (e.g., 15).
  • Strings format time as HH:MM:SS.milli or specific counts (e.g., '00:01:20').
  • Percentages evaluate relative to video length (e.g., '50%').
• folder: Path to the directory where files will save.
• filename: Format for file naming. Use %s to interpolate the specific frame's timestamp or %i for the index sequence.