Function set

resources/vega.min.js:350–352

(t, e)

      has: r,
      get: (t) => (r(t) ? n[t] : void 0),
      set(t, e) {
        return (r(t) || (++i.size, n[t] === lt && --i.empty), (n[t] = e), this);
      },
      delete(t) {
        return (r(t) && (--i.size, ++i.empty, (n[t] = lt)), this);
      },