How Can JavaScript Read and Write Files on Both the Server and Client Sides?

Reading and Writing Files with JavaScript

While it's generally not possible to perform file operations directly in a web browser, JavaScript offers capabilities for managing files on the server side through its Node.js implementation.

Server-Side File Manipulation

To read and write files using Node.js, utilize the fs (file system) module. Here's an example:

const fs = require('fs');

// Read a file
fs.readFile('file.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});

// Write a file
fs.writeFile('file.txt', 'Hello world!', err => {
  if (err) throw err;
  console.log('File has been written successfully.');
});

Client-Side File Manipulation

With HTML5, you can access files from the client side:

const fileInput = document.getElementById('file-input');

fileInput.addEventListener('change', e => {
  const file = e.target.files[0];

  // Read a file
  const reader = new FileReader();
  reader.onload = () => {
    console.log(reader.result);
  };
  reader.readAsText(file);

  // Write a file (client-side)
  const filename = 'file.txt';
  const fileContent = 'Hello world!';

  const blob = new Blob([fileContent], { type: 'text/plain' });
  const url = URL.createObjectURL(blob);

  const a = document.createElement('a');
  a.href = url;
  a.download = filename;
  a.click();
});

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