Basic JavaScript - Profile Lookup

[Philwil]

Tell us what’s happening:
Describe your issue in detail here.

One thing I really can’t understand about these functions is how does Javascript know to communicate [i] with the contacts list, I’m not sure I’m explaining my confusion. I can’t see how it connects to the list. I know i is arbitrary and declared as a variable starting at 0 and that it checks the contacts length and then does i++ if it hasn’t reached the end so then the i variable will = 1 then 2 etc but what actually tells Javascript that i++ means to iterate through the list?
I can’t complete any of these problems by myself because I don’t understand or know the syntax well enough and I don’t understand how some of these things actually work or function. I went through the course twice up until this point to check if I missed anything but some sections I understand and then one comes along that is totally out of my understanding.

  **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 (var 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
}

var data = lookUpProfile("Kristian", "likes");

console.log(data);

  **Your browser information:**

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Challenge: Basic JavaScript - Profile Lookup

Link to the challenge:

freeCodeCamp.org

[ilenia]

@Philwil

but what actually tells Javascript that i++ means to iterate through the list?

you say that

an array is accessed using bracket notation and index number, so if you have arr = ['apple', 'blue', 'November'], arr[0] will be 'apple', arr[1] will be 'blue' and 'November' for arr[2]. The index goes from 0 to arr.length - 1.

@Philwil

for (var i = 0; i < contacts.length; i++) {

A for loop written like this will iterate from 0 to arr.length - 1. Those are just numbers, JavaScript knows only that i is 0 at the start, and at each iteration increases by 1

You are telling it to use i to access the array when you write contacts[i]
when i equals 0 that eill be contacts[0], when i equals 1 that will be contacts[1] and so on

[Philwil]

Thank you Ilenia,
Makes perfect sense when you explain it so well.
I wish I could find more exercises/problems around the same concepts.
The course progresses a little quick from one exercise to the next. I’d need to do this kind of problem many times for the concepts to really sink in. Thanks for helping out!

[ilenia]

you could try solving katas on codewars, maybe 8th or 7th kyu, so you get the level of challenge you want