单例模式

单例模式

单列模式，一个构造函数一生只有一个实例

 const Person = (function () {
    function Person(name, age) {
      this.name = name;
      this.age = age;
    }
    let instance = null;
    return function singTom(arg) {
      if (!instance) instance = new Person(...arg);
      return instance;
    };
  })();
  const p1=new Person(['zhang',33]);
  const p2=new Person(['li',33]);
  console.log(p1,p2);
  console.log(p1==p2);//true