docs: function eachEvt(evt, handler, thisArg, cb) {
      "use strict";
      if (evt instanceof Array) {
          evt.forEach(evt => cb(evt, handler, thisArg));
          return true;
      }
      if (typeof evt === "object") {
          let realThisArg = handler;
          if (realThisArg === undefined) { realThisArg = null; }
          Object.entries(evt).forEach(([evt, handler]) => cb(evt, handler, realThisArg));
          return true;
      }
      return false;
  }