Function Set

docs/themes/htx/source/js/vue.js:568–570

()

    // a non-standard Set polyfill that only works with primitive keys.
    _Set = (function() {
      function Set() {
        this.set = Object.create(null);
      }
      Set.prototype.has = function has(key) {
        return this.set[key] === true;
      };