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.


This method is used to listen for events being dispatched.


  • type: Type of event; allowed values are: click and remove.
  • eventListener: The function that is executed when the event occurs.
  • useCapture: Boolean, and should be kept as false for now. Note: this value currently has no purpose.


void addEventListener(<DOMString> type, eventListener, <boolean> useCapture)


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

// Set the button's properties
var properties = {
  disabled: false,
  title: "My Test Extension",
  icon: "icon.18x18.png"

// Add the button to the browser UI
var button = opera.contexts.toolbar.createItem(properties);

// Update the button title each time the button is clicked
var i = 1;
button.addEventListener('click', handleClick, false);

function handleClick() {
  button.title = "You've clicked the button " + i + " time(s)";

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