runtime.onConnect
Fired when a connection is made with either an extension process or a content script.
Syntax
browser.runtime.onConnect.addListener(listener)browser.runtime.onConnect.removeListener(listener)browser.runtime.onConnect.hasListener(listener)Events have three functions:
addListener(listener)Adds a listener to this event.
removeListener(listener)Stop listening to this event. The
listenerargument is the listener to remove.hasListener(listener)Checks whether a
listeneris registered for this event. Returnstrueif it is listening,falseotherwise.
addListener syntax
Parameters
functionThe function called when this event occurs. The function is passed this argument:
portA
runtime.Portobject connecting the current script to the other context it is connecting to.
Examples
This content script:
- connects to the background script, and stores the
Portin a variablemyPort - listens for messages on
myPort, and logs them - sends messages to the background script, using
myPort, when the user clicks the document
// content-script.jslet myPort = browser.runtime.connect({ name: "port-from-cs" });myPort.postMessage({ greeting: "hello from content script" });myPort.onMessage.addListener((m) => { console.log("In content script, received message from background script: "); console.log(m.greeting);});document.body.addEventListener("click", () => { myPort.postMessage({ greeting: "they clicked the page!" });});The corresponding background script:
listens for connection attempts from the content script
when it receives a connection attempt:
- stores the port in a variable named
portFromCS - sends the content script a message using the port
- starts listening to messages received on the port, and logs them
- stores the port in a variable named
sends messages to the content script, using
portFromCS, when the user clicks the extension's browser action
// background-script.jslet portFromCS;function connected(p) { portFromCS = p; portFromCS.postMessage({ greeting: "hi there content script!" }); portFromCS.onMessage.addListener((m) => { console.log("In background script, received message from content script"); console.log(m.greeting); });}browser.runtime.onConnect.addListener(connected);browser.browserAction.onClicked.addListener(() => { portFromCS.postMessage({ greeting: "they clicked the button!" });});Browser compatibility
Note:This API is based on Chromium'schrome.runtime API. This documentation is derived fromruntime.json in the Chromium code.