Question

Here is the code:

// The Person constructor
function Person(name, age) {
    this.name = name;
    this.age = age;
}

// Now we can make an array of peoples
var family = new Array();
family[0] = Person("alice", 40);
family[1] = Person("bob", 42);
family[2] = Person("michelle", 8);
family[3] = Person("timmy", 6);

// loop through our new array
for ( i=0; i < family.length; i++; ) {
    console.log(family[i].name)
};

The expected output of this script is:

alice
bob
michelle
timmy

But the output is:

Uncaught TypeError: Cannot read property ‘name’ of undefined (anonymous function)

Answer 1

Add a new keyword for each Person added, and remove the extra ; in the for-loop (after the i++)

// Now we can make an array of people
var family = new Array();
family[0] = new Person("alice", 40);
family[1] = new Person("bob", 42);
family[2] = new Person("michelle", 8);
family[3] = new Person("timmy", 6);

// loop through our new array
for ( i=0; i < family.length; i++ ) {
    console.log(family[i].name);       // Also, added a semicolon here. Not required, but it's good practice to close your lines.
};

This will now log:

alice
bob
michelle
timmy