Profile look up (freecodecamp) challenge

Question

With this FreeCodeCamp problem I was stuck for ages but managed to get through it when I changed:

if(contacts[i].firstName === name)

to

if(contacts[i].name === firstName)

Not sure why switching name and firstName around worked, can someone explain why? update: added entire code for clarity:

//Setup
var contacts = [
    {
        "firstName": "Akira",
        "lastName": "Laine",
        "number": "0543236543",
        "likes": ["Pizza", "Coding", "Brownie Points"]
    },
    {
        "firstName": "Harry",
        "lastName": "Potter",
        "number": "0994372684",
        "likes": ["Hogwarts", "Magic", "Hagrid"]
    },
    {
        "firstName": "Sherlock",
        "lastName": "Holmes",
        "number": "0487345643",
        "likes": ["Intriguing Cases", "Violin"]
    },
    {
        "firstName": "Kristian",
        "lastName": "Vos",
        "number": "unknown",
        "likes": ["JavaScript", "Gaming", "Foxes"]
    }
];


function lookUpProfile(name, prop){
// Only change code below this line
for (var i =0; i <contacts.length; i++) {
    if(contacts[i].firstName === name) {
    if(contacts[i].hasOwnProperty(prop)) {
        return contacts[i][prop];
    } else
        return "No such property";   
    }
}
    return "No such contact"
// Only change code above this line
}

// Change these values to test your function
lookUpProfile("Akira", "likes"); 

Answer 1

I was thinking that. So this was the code that made me pass.

function lookUpProfile(name, prop){
// Only change code below this line
for (var i =0; i <contacts.length; i++) {
    if(contacts[i].firstName === name) {
    if(contacts[i].hasOwnProperty(prop)) {
        return contacts[i][prop];
    } else
        return "No such property";   
    }
}
    return "No such contact"
// Only change code above this line
}

// Change these values to test your function
lookUpProfile("Akira", "likes"); 

Answer 2

There are two issues with using the following if statement:

if(contacts[i].name === firstName)

The first issue is that you are trying to use firstName as a variable . There is no variable in your code called firstName and so you'll get an error when you try to use it as one. Instead, firstName is a property of an object in your array (not to be confused with a standalone variable). This means you can only access firstName with reference to an object in your array.

The second issue with the above code is contacts[i].name . In this part of your code contacts[i] is referring to the i th object in your code. You are then trying to access the name property of this given object. However, none of your objects have a name property - they have a firstName property, but don't have a name property. So, when you try and access a property/key that isn't in your object, you'll get undefined back.

The valid code to use is:

if(contacts[i].firstName === name)

as firstName is a property of your object (which you are accessing with reference to your object - contacts[i] ) and name is a variable (an argument of the function) which can be used without any problems.