opera.extension.addEventListener()

By Opera Software

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Description:

Registers a listener for an event specific to the popup window. The listener needs to use the standard EventListener interface - a function with an Event object as its first argument (e.g., var myListener = function(event){alert(event.type)}.

Parameters:

• type: The type of event to listen to.
• listener: The function that will be called
• useCapture: If true, the event listener is only added for the capture phase and target

Syntax:

void addEventListener (<DOMString> type, <EventListener> listener, UseCapture)

Example:

Listen for an incoming message from the background process. The source event is a messagePort to the connecting environment.

//
// The background process (e.g. '/background.js').
//

// Set options for the button
var UIItemProperties = {
  disabled: false,
  title: 'Opera Extension',
  icon: 'images/icon_18.png',
  popup: {
    href: 'popup.html',
    width: 500,
    height: 400
  },
  onclick: function() {
    opera.extension.broadcastMessage();
  }
};

// Create the button and add it to the toolbar
var button = opera.contexts.toolbar.createItem(UIItemProperties);
opera.contexts.toolbar.addItem(button);

//
// The popup script (e.g. '/popup.js').
//

// Note the "on" is removed from "onmessage" here
opera.extension.addEventListener('message', function(event) {
  document.write('Message received: ' + event.data);
}, false);

Note that this event listener can also be written using onmessage, as below.

// Create the button and add it to the toolbar
var button = opera.contexts.toolbar.createItem(UIItemProperties);
opera.contexts.toolbar.addItem(button);

//
// The popup script (e.g. '/popup.js').
//

opera.extension.onmessage = function(event) {
  document.write('Message received: ' + event.data);
};

This article is licensed under a Creative Commons Attribution 3.0 Unported license.