콘텐츠 스크립트를 통해 배경 스크립트에서 삽입된 스크립트로 통신을 설정하는 방법은 무엇입니까?

<code class="javascript">// Background script
function ensureSendMessage(tabId, message, callback) {
  chrome.tabs.sendMessage(tabId, { ping: true }, function (response) {
    if (response && response.pong) { // Content script ready
      chrome.tabs.sendMessage(tabId, message, callback);
    } else { // No listener on the other end
      chrome.tabs.executeScript(tabId, { file: "content_script.js" }, function () {
        if (chrome.runtime.lastError) {
          console.error(chrome.runtime.lastError);
          throw Error("Unable to inject script into tab " + tabId);
        }
        // OK, now it's injected and ready
        chrome.tabs.sendMessage(tabId, message, callback);
      });
    }
  });
}</code>

<code class="javascript">chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
  if (request.ping) {
    sendResponse({ pong: true });
    return;
  }
  // Content script action
});</code>

<code class="javascript">// Background script
function ensureSendMessage(tabId, message, callback) {
  chrome.tabs.executeScript(tabId, { file: "content_script.js" }, function () {
    if (chrome.runtime.lastError) {
      console.error(chrome.runtime.lastError);
      throw Error("Unable to inject script into tab " + tabId);
    }
    // OK, now it's injected and ready
    chrome.tabs.sendMessage(tabId, message, callback);
  });
}</code>

<code class="javascript">var injected;

if (!injected) {
  injected = true;
  // Your toplevel code
}</code>

<code class="javascript">chrome.tabs.query({}, function (tabs) {
  for (var i in tabs) {
    // Filter by URL if needed
    chrome.tabs.executeScript(tabs[i].id, { file: "content_script.js" }, function () {
      // Now you can use normal messaging
    });
  }
});</code>