构造函数有返回值,且为对象时

function Dog(name, age) {
            this.name = name;
            this.age = age;
            return {
                name: 'pan',
                age: 18
            }
        }
 console.log(new Dog('小黄', 2)) //   {name: "pan", age: 18}

上面代码可以看出构造函数有返回值且为对象时,会返回这个对象.