So I am learning recursion, starting with this challenge: Basic JavaScript: Use Recursion to Create a Countdown It presents this code: function countup(n) { if (n < 1) { return []; } else { const countArray = countup(n - 1); countArray.push(n); return countArray; } } console.…

Hello michaelnicol, This is the order that things happen: countup(5) -> else statement, countArray = countup(5 - 1 = 4) -> else statement, countArray = countup(3) -> else statement, countArray = countup(2) -> else statement, countArray = countup(1) -> else statement, countArray = countup(0) I…

So even though I call with (5) first, nothing happens until it reaches 1? Still slightly confused.

something happens alright, but the functions called can’t get an output till the function called isndie each one gets an output the only way for a function to get an output without waiting for the output of an other function is to trigger the base case if (n < 1) {return [];}, so now one function h…

countup(5) { const countArray = countup(4) { const countArray = countup(3) { const countArray = countup(2) { const countArray = countup(1) { const countArray = countup(0) { return []; countArray.p…

So basically, it keeps going down into more and more layers of scopes because no array is being returned. It then returns an empty array at 0, which then sends that array back up through all the arrays, pushing in the appropriate number.

Close. The base case returns []. The other cases return the result of countup(n-1) with the n pushed onto that array. countup(5) needs to know countup(4) before it can return.

In your written out example, how does const declaring the varaible not interfear scope wise? Shouldn’t it already be defined?

If I Googled correctly “The const declaration creates a read-only reference to a value. It does not mean the value it holds is immutable, just that the variable identifier cannot be reassigned. For instance, in the case where the content is an object, this means the object’s contents (e.g., its prop…

So I tried doing the challenge again with this new knowledge and I could not figure it out. I looked up the awnser and this is what I got: function sum(arr, n) { // Only change code below this line if (n <= 0) { return arr[0]; } return arr[n] + sum(arr,n-1) // Only change code above this line } I…

I think your code would return 5 when you call sum([2, 3, 4], 1). Is this what you are seeing/expecting?

A few questions about how Recursion works

Curriculum Help

joselvelez January 23, 2020, 9:42pm 13

michaelnicol,

I asked a similar question regarding this exercise as well. See this post:

This might help.

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A few questions about how Recursion works

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