onChanged

browser.commands.onChanged.addListener(listener)
browser.commands.onChanged.removeListener(listener)
browser.commands.onChanged.hasListener(listener)

Events have three functions:

addListener(listener)

Adds a listener to this event.

removeListener(listener)

Stop listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Check whether listener is registered for this event. Returns true if it is listening, false otherwise.

listener

The function called when a command's shortcut changes. The function is passed these arguments:

changeInfo

object. An object containing the name of the command, its new active shortcut, and its old shortcut.

name

string. Name of the command. This matches the name given to the command in its manifest.json entry.

newShortcut

string. The new active shortcut for this command, or blank if no shortcut is active.

oldShortcut

string. The shortcut that was active for this command, or blank if no shortcut was active.

You could log changes to command shortcuts like this:

function handleChanged(changeInfo) {
  console.log(`Shortcut for: ${changeInfo.name} changed`);
  console.log(`From: ${changeInfo.oldShortcut}`);
  console.log(`To: ${changeInfo.newShortcut}`);
}

browser.commands.onChanged.addListener(handleChanged);