To read data from a USB RS232 (serial) port using JavaScript, you have a few options depending on your use case and the environment in which your application runs. Let’s explore a couple of approaches:

1. Web Serial API (for modern browsers):
   • The Web Serial API allows websites to communicate with serial devices, including those connected via USB, directly from JavaScript.
   • It bridges the web and the physical world, enabling communication with microcontrollers, 3D printers, and other serial devices.
   • Here’s how you can use it:
     JavaScript

     // Check if the Web Serial API is supported
     if ("serial" in navigator) {
       // Prompt user to select any serial port
       const port = await navigator.serial.requestPort();
       // Set up the port (e.g., baud rate, buffer size)
       await port.open({ baudRate: 9600, bufferSize: 1024 });
       const reader = port.readable.getReader({ mode: "byob" });
     
       while (true) {
         const { value, done } = await reader.read(new Uint8Array(buffer));
         if (done) {
           break;
         }
         // Handle the received data in the 'value' buffer
       }
     }
     

     AI-generated code. Review and use carefully. More info on FAQ.
   • You can use this API to communicate directly with serial devices from your web application¹.
2. Node.js with WebSockets (for server-side applications):
   • If you’re building a server-side application using Node.js, you can read data from a USB serial port and broadcast it to a web application via WebSockets.
   • Here’s a high-level overview:
     • Install Node.js and necessary modules (e.g., serialport, ws).
     • Create a Node.js application that reads serial data and broadcasts it via WebSockets.
     • Load a web page that listens for WebSocket messages from the Node.js server.
     • Convert raw serial data (often transmitted in bytes) into a human-readable format.
   • Example code for reading data from a USB barcode scanner using Node.js and WebSockets:
     JavaScript

     // Node.js code snippet
     const SerialPort = require("serialport");
     const WebSocket = require("ws");
     
     const port = new SerialPort("/dev/ttyUSB0", { baudRate: 9600 });
     const wss = new WebSocket.Server({ port: 8080 });
     
     port.on("data", (data) => {
       // Broadcast data to connected clients via WebSockets
       wss.clients.forEach((client) => {
         if (client.readyState === WebSocket.OPEN) {
           client.send(data.toString()); // Convert buffer to string
         }
       });
     });
     

     AI-generated code. Review and use carefully. More info on FAQ.
   • Your web application can then handle the received barcode data as needed².

Remember that security considerations are crucial when accessing USB devices from a web application. Always ensure proper permissions and handle data securely. Choose the approach that best fits your requirements and environment!

Source: how javascript read out from usb rs232 – Search