Popup widget: “Uncaught TypeError: callback is not a function” in load_tlib()

Hi,

I found a JavaScript error in the popup widget (wp-content/plugins/gtranslate/js/popup.js):

Uncaught TypeError: callback is not a function

Cause

load_tlib() is used in two ways: it is called with a callback function, and it is also registered directly as an event listener:

e.addEventListener(‘pointerenter’, load_tlib);
e.addEventListener(‘focusin’, load_tlib);

When it is used as a listener, the browser passes the native Event object as the first argument. The current checks only test for truthiness (if (callback) and callback && callback()), and an Event object passes that test even though it is not callable.

This causes two problems:

1. If the library is already loaded (the else branch), callback() is called on a MouseEvent/FocusEvent and throws “callback is not a function”.
2. If the library is not loaded yet, the Event object is registered as a ‘load’ listener on the script element. It is not a valid listener (it has no handleEvent method), so an error is also reported when the script finishes loading.

Steps to reproduce

1. Open any page with the GTranslate popup widget.
2. Hover over the language switcher. This loads lib.min.js.
3. Move the pointer away and hover again, or tab into the switcher.
4. Check the browser console: “Uncaught TypeError: callback is not a function”.

Suggested fix

Check that the argument is actually a function before using it:

function load_tlib(callback) {
if (!window.gt_translate_script) {
window.gt_translate_script = document.createElement(‘script’);
gt_translate_script.src = ‘https://cdn.gtranslate.net/widgets/latest/lib.min.js’;
document.body.appendChild(gt_translate_script);
if (typeof callback === ‘function’)
gt_translate_script.addEventListener(‘load’, callback, {once: true});
} else {
if (typeof callback === ‘function’) callback();
}
}

Environment

• WordPress version: (local development)
• Widget type: Popup
• Reproduced in Chrome/Chromium; likely affects all browsers

Thanks!