Instantly share code, notes, and snippets.

Embed
What would you like to do?
Message passing of Chrome Extension example
/*****************************************************************
* 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;
});
{
"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'"
}
// 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)}`);
});
});
@rmetel

This comment has been minimized.

rmetel commented Jan 4, 2018

Thank you, that was helpful! ;)

@hlawuleka

This comment has been minimized.

hlawuleka commented Jan 29, 2018

When you say "// Send message from active tab to background: "

Then go ahead and say console.log(message from background: ${JSON.stringify(response)}); shouldn't your comment then say "Send message from background to active tab" ?

@antoniojtorres

This comment has been minimized.

antoniojtorres commented Jan 30, 2018

@hlawuleka - The console log is the response from the background script. The message that is being set is contained in the "p" object. Then the callback includes the response from the listener in the background script.

It would be more clear if it said, for example:

chrome.tabs.query({ active: true, currentWindow: true }, function(tabs) {  
  chrome.tabs.sendMessage(tabs[0].id, {message: 'Hello Background! How are you?'}, function(response) {  
    console.log('message from background:', response);  
   // Log: {message: 'Hello Tab!, I am doing swell!'}  
  });  
});
@rooton

This comment has been minimized.

rooton commented Aug 28, 2018

Maybe you know answer, when I send message from popup.js and background is inactive, then onMessage listener in background.js not fired. But when I send message from content-script.js, onMessage fired even if background is inactive mode.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment