Symbol

• 例1

    function Person(name, id) {
      this.name = name;
      this.id = id;
    }
    const p1 = new Person("JonSnow", 21);
    console.log(p1);

• 例2

    const Person = (() => {
      let _id = "";

      function P(name, id) {
        this.name = name;
        _id = id;
      }

      P.prototype.getId = function() {
        return _id;
      };

      return P;
    })();

    const p1 = new Person("JonSnow", 21);

    console.log(p1);
    console.log(p1.getId());

• 例3（使用Symbol实现属性私有化）

    const Person = (() => {
      const _id = Symbol("id");

      function P(name, id) {
        this.name = name;
        this[_id] = id;
      }

      P.prototype.getId = function() {
        return this[_id];
      };
      return P;
    })();
    const p1 = new Person("JonSnow", 21);

    console.log(p1);
    console.log(p1.getId());