In Chrome DevTools you can use getEventListeners(object) to get a list of registered event listeners on the specified object.

You can also do this without the console, by selecting an element in the DOM inspector. In the element details, select the tab Event Listeners".

Example

const registry = getEventListeners(document)

registry['up-click']
// 0: { useCapture: false, passive: false, once: false, type: 'up:click', listener: ƒ }
// 1: { useCapture: false, passive: false, once: false, type: 'up:click', listener: ƒ }
// ...
// length: n