class MySelf {
  constructor() {
    if (!MySelf.instance) {
      const data = Symbol();
      this[data] = {
        name: "Marshall Sun",
        university: "Northeastern University",
        company: "Bytedance",
        github: "https://github.com/Marshall-Sun",
      };
      this.introduce = () => console.table(this[data]);
      MySelf.instance = this;
    }
    return MySelf.instance;
  }
}