Why code return 3 values instead of 2

JavaScript
1

Why my code prints out 3 values instead of 2 (if I am right), given what pseudo-code I have

  function multiply(arr, n) {
    //extract the first element of the arr
    var product = arr[0];
    for (var i = 1; i <= n; i++) {
      //iterate over i starting from 1 unless it is less than equal to n
      //n = 3
      //1 , 1 <= 3 //false
      //2 , 2 <=3 //false
      //3 , 3 <= //true
     console.log(arr[i])
        //product *= arr[i];
    }
    //return product;
  }
  console.log(multiply([1,2,5,6,7,8], 3));
//output 2,5,6

It is part of this, where I m trying to understand what the example says.

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Challenge: Replace Loops using Recursion

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2

It prints 3 values because your if statement says to start counting from 1 and keep going until it reaches 3.
Therefore, when we count from 1 to 3 we say: 1, 2, 3
That’s three things.

If you want it to print 2 things you can say to count from 1 to less than 3 which is the same as 1, 2 for example. Or you can just pass it 2 into the parameter ‘n’.

Does this help?

3

The i <=n in your loop means “keep doing this as long as i <= n is true”.
1 <= 3 is true. The loop executes.
2 <= 3 is true. The loop executes.
3 <= 3 is true. The loop executes.
4 <= 4 is false. The loop exits.

4

oh now I see. :man_facepalming: how can I not see.

5

We all have brainfarts sometimes. :smiley:

6

As I am reading the question, I cannot run the following code

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

are we suppose to understand it? As I am having difficulty understanding it.

7

What do you mean by you can’t run it? What part of the example code do you not understand?

function multiply(arr, n) {
  // assign first array element to product
  var product = arr[0];
  // loop n times starting at 1
  for (var i = 1; i <= n; i++) {
    // multiply product with the current array element, using shorthand
    // same as product = product * arr[i];
    product *= arr[i];
  }
  return product;
}

console.log(multiply([2, 3, 4], 2));
// 24
// 2 * 3 === 6
// 6 * 4 === 24
8

@lasjorg I tried running it, it gave me NaN.

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

  multiply([1,2,3], 10)

I find it hard to break it down to find out what is going on :sob:

9

You are passing in 10 as an argument to the function but the array is not that long. Do you not understand what the second parameter (n) does?

10

Not sure if this example is super helpful, but it might at least show the use of the n parameter in a different context.

function inviteGuests(guests, numberOfGuests) {
  // Let make sure we have at least one guest, otherwise it is a lame party
  let guestList = guests[0];
  // loop numberOfGuests times starting at 1
  for (let i = 1; i < numberOfGuests; i++) {
    // Do some string concatenation
    guestList += ', ' + guests[i];
  }
  return guestList;
}


console.log(inviteGuests(['Jack', 'Matt', 'Jenny', 'Paula', 'Benny', 'John', 'Anna'], 2));
//  Jack, Matt
console.log(inviteGuests(['Jack', 'Matt', 'Jenny', 'Paula', 'Benny', 'John', 'Anna'], 4));
// Jack, Matt, Jenny, Paula
console.log(inviteGuests(['Jack', 'Matt', 'Jenny', 'Paula', 'Benny', 'John', 'Anna'], 6));
// Jack, Matt, Jenny, Paula, Benny, John