Profile Lookup for loop condition query

JavaScript
1

Tell us what’s happening:
I’ve solved the problem, but I’m curious about one aspect of the code.

When my for loop iterates with the condition “i <= contacts.length”, it fails the test. Why? My assumption is that by setting i equal to the length of the array, JS detects something that isn’t there? However, I’m going to look this up but I thought I’d ask you all as well.
Thanks,
Nick

  **Your code so far**


// Setup
const 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(let i = 0;i < contacts.length; i++){
  if(contacts[i].firstName === name){
    return contacts[i][prop] || "No such property";
  } 
  } return "No such contact";
   

// Only change code above this line
}

lookUpProfile("Akira", "likes");

  **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36

Challenge: Profile Lookup

Link to the challenge:

2

Lets look at a smaller example:

const myArr = [0, 1, 2, 4, 8, 16];
for (let i = 0; i <= myArr.length; i++) {
  console.log(myArr[i]);
}

What do you see when you run this code?

Once you know that, then you should look at what happens if you try to access a property of myArr[myArr.length].

3

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