elementExists(cssSelector, msg = true) {
    const el = document.querySelector(cssSelector);
    let exists = false;
    if (el !== null) exists = true;
    if (msg === true) {
      this.send({
        payload: exists,
        info: 'Element "'.concat(cssSelector, '" ').concat(exists ? "exists" : "does not exist")
      });
    }
    return exists;
  }
Does the chosen CSS Selector currently exist?
Automatically sends a msg back to Node-RED unless turned off.
@param {string} cssSelector Required. CSS Selector to examine for visibility
@param {boolean} [msg] Optional, default=true. If true also sends a message back to Node-RED
@returns {boolean} True if the element exists