Removing all video inside of the youtubes watch later playlist.

clearWatchLater.js

var clearTimer;
function clearWatchList(interval) {clearTimer = setInterval(clearWatchLater, interval);}
function clearWatchLater(buttonName, fieldName) {
    document.querySelector('#primary button[aria-label="Aktionsmenü"]').click();
var things = document.evaluate('//span[contains(text(),"Später ansehen")]',document,null,XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,null);
    if (things.snapshotLength = 0) {killSwitch()}
    for (var i = 0; i < things.snapshotLength; i++) {
        things.snapshotItem(i).click();
    }
}
function killSwitch() {
  clearInterval(clearTimer);
}