By Opera Software

From Opera 15 onward, Opera 11 & 12’s extension format is no longer supported, and instead, we’ve switched to Chromium’s extension model. Check out our new documentation for developing extensions for Opera 15 and higher and start building your own extensions.


The readonly closed attribute exposes the closed state of the browser window. On getting, the closed attribute returns true if the browser window has been closed, otherwise, it returns false.


readonly boolean closed


The following example creates a button on the browser toolbar. When the button is clicked, the closed state of the last focused window is detected. If it is not closed, the script closes the window.

// The background process (e.g. index.html)

// Specify the properties of the button before creating it.
var UIItemProperties = {
  disabled: false,
  title: "Example extension",
  icon: "images/icon_18.png",
  badge: {
    backgroundColor: '#cc0000',
    color: '#ffffff'

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

button.addEventListener('click', handleClick, false);

function handleClick() {
  // Get the last focused window
  var thisWin =;

  // If the window is not closed, close it
  if (thisWin.closed === false) {

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


No new comments accepted.