NodeJS recursion with dynamic number of parameters

Question

I'm never to NodeJS and therefore struggling with a recursive multiplication function. The problem seems to be that in the recursion the input parameters are an array which is then assigned to the first value instead of value by value. Here's the code

const multiply = (factor1, ...factors) => {
  if (factors.length > 1){
    return Math.round(factor1 * multiply(factors) * scale) / scale;
  }
  const factor2 = factors[0];
  return Math.round(factor1 * factor2 * scale) / scale;
}

so calling with: multiply(1,1,1,1) leads to:

iteration: factor1: 1, factors: [1,1,1]
iteration: factor1: [1,1,1], factors: Array(0)

how can I achieve to have in the second iteration factor1: 1, factors: [1,1], without checking if factor1 is an array?

James · Accepted Answer · 2019-11-08T11:08:06.910

1

The issue is when you recursively call multiply, you don't pass each number as a separate parameter, you pass factors which is an array, therefore multiply gets a single array parameter.

Two ways of fixing this, either using the spread syntax

 multiply(...factors)

Or you can use apply to invoke multiply and pass the parameters as an array

 multiply.apply(null, factors)

edited Nov 08 '19 at 11:08

answered Nov 08 '19 at 10:52

James

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unfortunately not, factors in the second iteration becomes now an array of arrays.. – fsulser Nov 08 '19 at 11:00
@fsulser sorry, yeah, can see why, I misread. Let me update... – James Nov 08 '19 at 11:02
I think the first one would still lead to the same problem. But using apply seems to be the solution. Thank you James – fsulser Nov 08 '19 at 12:26
@fsulser have you tried using the spread operator? It should be fine :) – James Nov 08 '19 at 18:05

NodeJS recursion with dynamic number of parameters

1 Answers1