Edit in JSFiddle

function Person(name, age) {
  this.name = name;
  this.age = age;
  this.sayName = new Function('document.write(this.name);'); // 논리적으로 같음
}

var person1 = new Person("nam", 33);
var person2 = new Person("sin", 27);

person1.sayName(); // nam
document.write("<br>");
person2.sayName(); // sin
document.write("<br>");
document.write(person1.showInfo == person2.showInfo); // false