function Person(name , age , job){
this.name = name;
this.age = age;
this.job = job;
this.sayName = function(){
alert(this.name);
};
}
var person1 = new Person("aaa",29,"singer");
var person2 = new Person("bbb",30,"doctor");
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person1 = Person {name: "aaa", age: 29, job: "singer"};
person1.name = "aaa";