How to sleep in a firefox extension (old and native JS methods not working)?

Question

I tried

let { setTimeout } = require('sdk/timers');
browser.webNavigation.onCompleted.addListener(setTimeout(resetSpeed, 3000));
browser.webNavigation.onHistoryStateUpdated.addListener(setTimeout(resetSpeed, 3000));
(...)

it didn't work. Another try:

browser.webNavigation.onCompleted.addListener(resetSpeed);
browser.webNavigation.onHistoryStateUpdated.addListener(resetSpeed);

function resetSpeed() {
  await new Promise(r => setTimeout(r, 2000)); 
(...)

That didn't work also.

Without the sleep function, my code used to automatically speed up audio/videos on page load works ~25% of the time, and 100% of the time when I run it with my custom key-press combination. I want to add sleep functionality to get it to 100% as I think it runs way too quickly.

My permissions:

  "permissions": [
    "contextMenus",
    "tabs",
    "<all_urls>",
    "http://*/*",
    "https://*/*",
    "file:///*/*",
    "webNavigation"
  ]

Answer 1

Nevermind. Adding async fixed it.

browser.webNavigation.onCompleted.addListener(resetSpeed);
browser.webNavigation.onHistoryStateUpdated.addListener(resetSpeed);

async function resetSpeed() {
  await new Promise(r => setTimeout(r, 2000)); 
(...)