Message passing of Chrome Extension example

background.js

/*****************************************************************
 * onMessage from the extension or tab (a content script)
 *****************************************************************/
chrome.runtime.onMessage.addListener(
  function(request, sender, sendResponse) {
    if (request.cmd == "any command") {
      sendResponse({ result: "any response from background" });
    } else {
      sendResponse({ result: "error", message: `Invalid 'cmd'` });
    }
    // Note: Returning true is required here!
    //  ref: http://stackoverflow.com/questions/20077487/chrome-extension-message-passing-response-not-sent
    return true; 
  });

manifest.json

{
  "name": "example",
  "version": "0.0.1",
  "description": "Chrome Extension's message passing example",
  "permissions": [
    "<all_urls>",
    "webRequest",
    "webRequestBlocking",
    "background",
    "activeTab"
  ],
  "background": {
    "scripts": ["background.js"]
      // "persistent": false
  },
  "content_scripts": [{
    //"matches": ["http://*/*"],
    // "css": ["mystyles.css"],
    "js": [
      "extlib/js/jquery.min.js",
      "content.js"
    ]
  }],
  "browser_action": {
    "default_title": "hoge",
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "manifest_version": 2,
  "content_security_policy": "script-src 'self' https://ajax.googleapis.com https://maxcdn.bootstrapcdn.com/; object-src 'self'"
}

popup.js

// If you want to sendMessage from any popup or content script,
// use `chrome.runtime.sendMessage()`.

// Send message to background:
chrome.runtime.sendMessage(p, function(response) {
  console.log(`message from background: ${JSON.stringify(response)}`);
});


// If you want to sendMessage from tab of browser,
// use `chrome.tabs.sendMessage()`.

// Send message from active tab to background: 
chrome.tabs.query({ active: true, currentWindow: true }, function(tabs) {
  chrome.tabs.sendMessage(tabs[0].id, p, function(response) {
    console.log(`message from background: ${JSON.stringify(response)}`);
  });
});