构造函数为什么不生效？

Question

function Person(name,age,job) {       this.name=name;// 要用构造函数起名时候要首字母大写      this.age=age;    this.job=job;    this.sayName=function () {        alert(this.name);    };}var person3=new Object("Nicholas",29,"Software Engineer");var person4=new Object('Greg',27,"Doctor");console.log(person3.name); // undefinedconsole.log(person3.constructor==Person); //falseconsole.log(person4.constructor==Person); //falseconsole.log(person3 instanceof Object); //trueconsole.log(person3 instanceof Person); //falseconsole.log(person4 instanceof Object); //trueconsole.log(person4 instanceof Person); //false