Method _handlerIndex

resources/vega.min.js:14196–14200

(t, e, n)

    on() {}
    off() {}
    _handlerIndex(t, e, n) {
      for (let r = t ? t.length : 0; --r >= 0; )
        if (t[r].type === e && (!n || t[r].handler === n)) return r;
      return -1;
    }
    handlers(t) {
      const e = this._handlers,
        n = [];