Learn Introductory JavaScript by Building a Pyramid Generator - Step 24

JavaScript
1

Tell us what’s happening:

" You should update the last element of the cities array to the string “Mexico City”. Remember that you can access the last element of an array using array[array.length - 1]. "

I don’t understand how/where to use array.length:

Your code so far

let character = 'Hello';
let count = 8;
let rows = ["Naomi", "Quincy", "CamperChan"];

// User Editable Region

let cities = ["London", "New York", "Mumbai"];

let cities = ["London", "New York", "Mexico City"];

console.log(cities);


// User Editable Region

console.log(rows);

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Challenge Information:

Learn Introductory JavaScript by Building a Pyramid Generator - Step 24

2

instead of trying to redeclare the cities variable with another different array,
they would like you to mutate the array.
So after the first line that declared cities, if I wanted to change the first value in the array, I would write:
cities[0] = 'Toronto';

Hopefully you recall this indexing method?
So if you know that length is the length of the array, how can you do something similar to what I did but target the last value in the array instead?

3

" You should update the last element of the cities array to the string "Mexico City" . "

If my brain’s working right then: “you should update the last element of the ‘cities’ array to the string.”
Then, ‘last element’ meaning Mumbai? And I then have to change it to Mexico City? .–.

4

yes the -value- of the last element is Mumbai initially.
What’s its index though? (try to use length to describe it)

5

" Remember that you can access the last element of an array using array[array.length - 1] ."
the length must be 1, but the whole array[array.length - 1] confuses me and I don’t understand it at all, as much as I tried thinking nothing lights up.

6

what if you try adding this line of code just after your cities line
console.log(cities.length);

what do you think that would print out?
how about
console.log(cities[cities.length-1]);

7

So, i’m trying to divide everything.

array = cities

console.log(cities[length-1]);

console.log allows me to output messages or values to the console

an array stores multiple values and elements in one variable. These values can be of any data type — meaning I can store a string, number, boolean, and other data types in one variable.

[length - 1] will help me access the last element of the array (cities), which for me is Mumbai.

but console.log(cities[length-1]); should print something. Which I sadly still can’t be able to understand

Can you please give me a slightly different example?

8

cities is a variable yes.
You’ve defined it already here:

The square bracket notation you used indicates an array type.
The array has 3 values.
The array is zero-indexed. Meaning, the first value is considered the zero-th value, the second is the first, the third is the second (confusing but true).
The values in the array can be accessed with bracket notation like:
cities[0] to get London
cities[1] to get New York etc.

The bracket notations wants a number to be in it. (an index is a number)

What is cities.length? it is a number (earlier I wrote the code wrong, I will fix it soon. I forgot the cities. part)

What is cities.length - 1, that is also a number etc.

9

Can you show me a visual example?

10

please read this

12

mod edit: code removed

Thank you for sticking around and explaining everything to me without revealing the answer. Considering it took me 4 whole hours to understand one test I got it in the end thanks to you!

13

no problem at all.
I removed the code solution as we want people to read this thread and work out the answer for themselves.
Hope you find arrays easy now!

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