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(callback)

Adds a listener to this event.

removeListener(listener)

Stop listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Checks whether a listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

function

A callback function that will be called when this event occurs. The function will be passed the following arguments:

port

A runtime.Port object connecting the current script to the other context it is connecting to.

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Examples

This content script:

• connects to the background script, and stores the Port in a variable myPort
• listens for messages on myPort, and logs them
• sends messages to the background script, using myPort, when the user clicks the document

// content-script.js
var myPort = browser.runtime.connect({name:"port-from-cs"});
myPort.postMessage({greeting: "hello from content script"});
myPort.onMessage.addListener(function(m) {
  console.log("In content script, received message from background script: ");
  console.log(m.greeting);
});
document.body.addEventListener("click", function() {
  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
• sends messages to the content script, using portFromCS, when the user clicks the extension's browser action

// background-script.js
var portFromCS;
function connected(p) {
  portFromCS = p;
  portFromCS.postMessage({greeting: "hi there content script!"});
  portFromCS.onMessage.addListener(function(m) {
    console.log("In background script, received message from content script")
    console.log(m.greeting);
  });
}
browser.runtime.onConnect.addListener(connected);
browser.browserAction.onClicked.addListener(function() {
  portFromCS.postMessage({greeting: "they clicked the button!"});
});

Example extensions

• embedded-webextension-sdk

// Copyright 2015 The Chromium Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.