javascript - 我的 JavaScript 代码出了什么问题

Question

这是我正在做的练习:http://www.codecademy.com/courses/building-an-address-book/0/3?curriculum_id=506324b3a7dffd00020bf661#

Here is my code:

var bob = {
    firstName: "Bob",
    lastName: "Jones",
    phoneNumber: "(650) 777-7777",
    email: "bob.jones@example.com"
};

var mary = {
    firstName: "Mary",
    lastName: "Johnson",
    phoneNumber: "(650) 888-8888",
    email: "mary.johnson@example.com"
};

var contacts = [bob, mary];

// printPerson added here
function printPerson(person){
    console.log(firstName);
    console.log(lastName);
};

function printPerson(){
        console.log(contacts[0]);
}
function printPerson(){
        console.log(contacts[1]);
}

Answer 1

var bob = {
    firstName: "Bob",
    lastName: "Jones",
    phoneNumber: "(650) 777-7777",
    email: "bob.jones@example.com"
};

var mary = {
    firstName: "Mary",
    lastName: "Johnson",
    phoneNumber: "(650) 888-8888",
    email: "mary.johnson@example.com"
};

var contacts = [bob, mary];

// printPerson added here
function printPerson(person){
    console.log(person.firstName + " "+ person.lastName);   
}

printPerson(contacts[0]);
printPerson(contacts[1]);