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`
   ```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
&nbsp;

- download a file with https and fs module
  ```js
  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);
	  });
	
  ```


&nbsp;


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

&nbsp;
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](../../../_resources/Comprehensive%20Guide%20to%20Better-SQLite3%20%2816_5_2026%205.html)
for parameterized query, string concatenation using `||`
```js
 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  '% '|| ? || '%'`;
```

&nbsp;

generate thumbnails of video
```js
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
```js
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.