Basic JavaScript - Replace Loops using Recursion

JavaScript
1

I don’t understand why at some point there is [ n - 1] in the example for the loop

I coppie the example here and can’t seem to find or understand at what point I would know that minus 1 comes in. So I don’t understand how I would know to put minus 1 when doing a recursive problem like this. Can someone please explain where the minus 1 comes from ?

I hope I explained my question well

 function multiply(arr, n) {
    let product = 1;
    for (let i = 0; i < n; i++) {
      product *= arr[I];
    }
    return product;
  }

Then this is what the recursive would be

  function multiply(arr, n) {
    if (n <= 0) {
      return 1;
    } else {
      return multiply(arr, n - 1) * arr[n - 1];
    }
  }

function sum(arr, n) {
  // Only change code below this line

  // Only change code above this line
}

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Challenge: Basic JavaScript - Replace Loops using Recursion

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2

The best way to see what is happening here is to use a real life example.

multiply([4,5,6], 2)

Replace the variables in that return statement with their actual values.

2 Likes
3

Thank you I’m going to try that.

1 Like