Basic JavaScript - Replace Loops using Recursion

JavaScript
1

hello good day. i can’t seem to get past this challenge. pls what should i do here?

the hint couldn’t help either. thanks.

Your code so far

function sum(arr, n) {
  // Only change code below this line
if (n == 1 ) {
return n + 1;
 } else { 
   return arr + sum(arr, n + 1);
 }
  // Only change code above this line
}

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Challenge: Basic JavaScript - Replace Loops using Recursion

Link to the challenge:

2

What do you intend this to mean?

3

i was thinking i needed to add + 1 to calc for the next arr value cause it says sum but looking at it now…i really do not know?

4

I think you should be focusing more on what do you expect the computer to do
when you say

arr + something

for eg. what would

arr + 2 give us?

5

let arr = 1 will give us 3.

6

Hold up for a second. Is arr a number?

7

i think so? is it not representing the unknown n value? or does it just stand for array?

sorry recursion is giving me a tough time…could you please explain in the simplest form that could help me understand.

8

Write a recursive function, sum(arr, n), that returns the sum of the first n elements of an array arr.

What is n? What is arr?

It isn’t really possible to get the answer without understanding what the inputs are.

9

arr is an array of numbers and n is the numbers in the array.

10

provided that you know that an array of numbers is NOT the same thing as a single number…

what does arr + 1 give us?

11

array would have to be arr = [1 , 2]

12

But you cannot add a number and an array, so that syntax can’t work.

So, lets back up here.

What should sum(arr, 5) do?

13

sum the array data up till the fifth value.

14

That’d be pretty easy if you had the answer to sum(arr, 4) right?

15

yeah.
sum(arr, 5) should return sum of arr(n - 1) till the fifth value.

16

Did you see what I last posted?

I mean, finding the answer to sum(arr, 5) would be pretty easy if you already knew the answer to sum(arr, 4), right?

17

ok i’m confused. can we start from scratch. like what is arr? i’m asking.

18

arr is a data structure called an array.

It is like a list of values.

It is denoted this way
[1,2,3,4,5]
or
["an","array","of","strings"]

Here’s the step that talks about arrays in the curriculum

If you go and look at that one and the following 3 or 4 steps, you can refresh your memory about arrays there.

19

arr is still an array of numbers

You said that sum(arr, 5) should

Wouldn’t finding the sum of the first 5 elements be really easy if you already knew the sum of the first 4 elements?

20

yeah.
so you’re trying to say that sum(arr, 4) = the sum of the array data till the fourth value?