Embraz
1
function countup(n) {
if (n < 1) {
return [];
} else {
const countArray = countup(n  1);
countArray.push(n);
return countArray;
}
}
console.log(countup(5));
Please I don’t understand how this returns [1,2,3,4,5] instead of [4,3,2,1] as I am thinking cos the number ’ n ‘ ought to be decreasing (n1)
Two questions for you to think about

What is countup(4)
supposed to return

What happens if you push 5 onto that result
Embraz
3
I still don’t understand this. Please Can you explain the code in your own words. Thanks
Embraz
4
The logic please using n = 5. Thank you
Can you please try to answer the two questions I asked?
I understand that the code may seem confusing at first. Let’s break it down step by step.
The countup
function takes a parameter n
and returns an array of numbers starting from 1 up to n
.
Here’s how it works:
 When
countup
is called with a value of n
, it checks if n
is less than 1 (n < 1
).
 If
n
is less than 1, it means we’ve reached the base case, and the function returns an empty array []
.
 If
n
is not less than 1, it means we need to continue counting up.
 In this case, the function recursively calls itself with
n  1
as the argument: countArray = countup(n  1)
.
 The recursive call will continue until it reaches the base case, where
n
is less than 1.
 Once the base case is reached, the recursive calls start returning, and each call adds its respective
n
value to the countArray
.
 Finally, the function returns the
countArray
, which now contains all the numbers from 1 to n
in ascending order.
So, when you call countup(5)
, it goes through the recursive calls as follows:

countup(5)
calls countup(4)

countup(4)
calls countup(3)

countup(3)
calls countup(2)

countup(2)
calls countup(1)

countup(1)
returns an empty array []

countup(2)
adds 2
to the array and returns [2]

countup(3)
adds 3
to the array [2]
and returns [2, 3]

countup(4)
adds 4
to the array [2, 3]
and returns [2, 3, 4]

countup(5)
adds 5
to the array [2, 3, 4]
and returns [2, 3, 4, 5]
That’s why the output is [1, 2, 3, 4, 5]
instead of [4, 3, 2, 1]
.
I hope this explanation helps clarify how the code works. If you have any more questions, feel free to ask!
Embraz
8
Just the explanation I needed. I’m immensely grateful. Thank you very much. I now understand the logic
Embraz
9
Thanks you. I think I’ve understood it
Embraz
10
Thank you. I think I’ve understood it. I’m grateful
system
Closed
11
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