How to multiply odd index?

Question

I have a little problem with my Javascript code. Here is my question :

I want to write a function, who take in input a table of numbers. If numbers situated in even index, be returned as the way it is. But, if numbers situated in odd index, be return multiplied by his index.

For example :

Input :

[5, 10, 15, 20, 25, 30, 50, 100]

Return :

[5, 10, 15, 60, 25, 150, 50, 700]

So, my code :

function multiplyNum(numbers) {
  const multiply = numbers.map(function(number) {
      for (let i = 0; i < numbers.length; i++) {
        if (numbers[i] % 2 == 0) {
          return numbers
        }
        if (numbers[i] % 2 !== 0) {
          return numbers
        }
      });
    return multiplyNum
  }

I'm not sure I see anywhere in your code where you're multiplying anything. I only see you using the mod operator. Am I just not seeing the multiplication? Also, you're comparing your values in two different ways. One way, you're doing a "double equals check" and the other, a "triple equals check". That is, you're doing an identity check in one and an equality check in another. Take a look at this -- https://stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons Note: That's not gonna solve the problem here but consistency is good. — rudolph schmitz, Oct 05 '18 at 19:52
You have unbalanced braces. And you should return `multiply`, not `multiplyNum`. — Barmar, Oct 05 '18 at 20:25

Zakaria Acharki · Accepted Answer · 2018-10-05T20:48:16.877

3

You don't need the for loop at all, you can get the index from the map and multiply the odd values:

function multiplyNum(numbers) {
  return numbers.map(function(number, index) {
    return index % 2 ? number * index : number;
  });
}

console.log(multiplyNum([5, 10, 15, 20, 25, 30, 50, 100]));

edited Oct 05 '18 at 20:48

answered Oct 05 '18 at 19:54

Zakaria Acharki

66,747
15
75
101

Actually, you're checking if the number is odd instead of the index. – naeramarth7 Oct 05 '18 at 20:33
Thanks for your Intervention @naeramarth7 , fixed now – Zakaria Acharki Oct 05 '18 at 20:49

score 2 · Answer 2 · answered Oct 05 '18 at 19:55

2

You could map with a conditional operator as a check.

var array = [5, 10, 15, 20, 25, 30, 50, 100],
    result = array.map((v, i) => i % 2 ? v * i : v);

console.log(result);

answered Oct 05 '18 at 19:55

Nina Scholz

376,160
25
347
392

How to multiply odd index?

2 Answers2