onSelectionChanged

Fires when the user selects a different page element for inspection with the browser's developer tools, for example by selecting the "Inspect Element" context menu item in Firefox.

browser.devtools.panels.elements.onSelectionChanged.addListener(listener)
browser.devtools.panels.elements.onSelectionChanged.removeListener(listener)
browser.devtools.panels.elements.onSelectionChanged.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.

callback

Function that will be called when this event occurs. The function will be passed no arguments.

Listen for selection changed events, and log the text content of the newly selected element:

function handleSelectedElement() {
  browser.devtools.inspectedWindow.eval("$0.textContent")
    .then((result) => {
      console.log(result[0]);
    });
}

browser.devtools.panels.elements.onSelectionChanged.addListener(handleSelectedElement);