runtime.onConnect

browser.runtime.onConnect.addListener(listener);
browser.runtime.onConnect.removeListener(listener);
browser.runtime.onConnect.hasListener(listener);

事件有三个方法：

addListener(callback)

为 这个事件添加一个监听器。

removeListener(listener)

停止监听这个事件。listener 参数就是要移除的监听器。

hasListener(listener)

检查监听器是否已经注册到这个事件上。如果已经监听，则返回 true 否则返回 false.

function

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

port

A runtime.Port (en-US) object connecting the current script to the other context it is connecting to.

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!" });
});