How to Remove Orphaned Script After Chrome Extension Update?

How to Remove Orphaned Script After Chrome Extension Update

Problem:

When a Chrome extension is reloaded, orphaned content scripts can remain, leading to errors and communication issues with other parts of the extension. This issue occurs if the original content script has DOM event listeners, preventing its automatic removal.

Solution:

To remove the orphaned script:

1. Send a message from the new, working content script to the orphaned script using Window.
2. Upon receiving the message, the orphaned script should unregister all listeners and global variables. This will make it eligible for garbage collection.

Code Example:

background.js:

<code class="javascript">// Re-inject content scripts on reloading/installing the extension
// (See example in link provided in QA)</code>

content.js:

<code class="javascript">// Generate a unique message ID for the orphan check
const orphanMessageId = chrome.runtime.id + 'orphanCheck';

// Register a listener for the orphan check message
window.addEventListener(orphanMessageId, unregisterOrphan);

// ... (Continue with original content script code) ...

// Function to unregister the orphaned script
function unregisterOrphan() {
  // Check if the extension is uninstalled
  if (!chrome.runtime.id) {
    // The script is not orphaned
    return;
  }
  
  // Remove the orphan message listener
  window.removeEventListener(orphanMessageId, unregisterOrphan);

  // Remove DOM event listeners
  document.removeEventListener('mousemove', onMouseMove);

  // Remove runtime message listener (try-catch required in some cases)
  try {
    chrome.runtime.onMessage.removeListener(onMessage);
  } catch (e) {}
}</code>

popup.js:

<code class="javascript">// Function to send a message and ensure a content script is injected before doing so
async function sendMessage(data) {
  const [tab] = await chrome.tabs.query({ active: true, currentWindow: true });
  if (await ensureContentScript(tab.id)) {
    return await chrome.tabs.sendMessage(tab.id, data);
  }
}

// Function to check if a content script is running and re-inject it if not
async function ensureContentScript(tabId) {
  try {
    // Check if the content script is running
    const [{ result }] = await chrome.scripting.executeScript({
      target: { tabId },
      func: () => window.running === true,
    });
    
    // If not, inject the content script
    if (!result) {
      await chrome.scripting.executeScript({
        target: { tabId },
        files: ['content.js'],
      });
    }
    
    return true;
  } catch (e) {}
}</code>

With this approach, the orphaned script will be cleaned up and communication with the rest of the extension can be restored.

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