Node Readline Module Does Not Have An End Event How Can I Do Something When There Are No More Lines

When using Node.js for your projects, you might encounter situations where you wish to perform a specific action when all lines have been processed but there's no built-in "end" event available in the Readline module. However, worry not, as there are alternative ways to achieve your desired functionality. Let's dive into some practical solutions.

One common approach to tackle this issue is by harnessing the power of Node's built-in 'close' event. This event is triggered when the input stream has ended, allowing us to execute our desired logic at the appropriate moment. By listening to this event, we can effectively mimic the behavior of an 'end' event.

Let's take a closer look at how we can implement this technique in your code:

Javascript

const readline = require('readline');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false
});

rl.on('line', (line) =&gt; {
  // Process each line as needed
  console.log(`Received line: ${line}`);
});

rl.on('close', () =&gt; {
  // Perform actions when all lines have been processed
  console.log('All lines have been read. Performing final tasks...');
  // Add your custom logic here
});

In the code snippet above, we've utilized the 'close' event to handle the scenario where all lines have been read. Within the event handler, you can include any additional operations or functions that need to be executed upon completion of reading all lines.

Another way to address this issue is by explicitly checking for the 'SIGINT' (Signal Interrupt) event, which is sent to a Node process when you manually interrupt it using 'Ctrl + C' in the terminal. By associating your end-of-processing logic with this event, you can ensure that your code responds appropriately when the user decides to terminate the input stream prematurely.

Here's an example of how you can incorporate the 'SIGINT' event check into your Readline module code:

Javascript

process.stdin.on('end', () =&gt; {
  // Perform actions when no more lines are available
  console.log('No more lines to read. Exiting...');
  // Add any final tasks or cleanup operations here
});

process.on('SIGINT', () =&gt; {
  // Handle user interruption (Ctrl + C)
  console.log('Process manually interrupted. Performing cleanup...');
  process.exit();
});

By implementing this method, you can ensure that your application responds gracefully to interruptions and concludes its operations cleanly.

In conclusion, while the Node Readline module may not provide a native 'end' event, you can leverage alternative events such as 'close' and 'SIGINT' to achieve similar functionality. By incorporating these event handlers into your code, you can effectively manage the completion of line processing and execute custom routines when all lines have been read.

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