ES6 字符串原型属性 prototype

function employee(id, name) {
   this.id = id;
   this.name = name;
}
var emp = new employee(123, "Smith");
employee.prototype.email = "smith@abc.com";

console.log("Employee 's Id: " + emp.id);
console.log("Employee's name: " + emp.name);
console.log("Employee's Email ID: " + emp.email);