Thriv Times 1/2023

thriv-times-2023-01.js

// Short answer, which fails on erroneous input.
const sumOfEveryOther = number => 
  number.toString().match(/\d/g)
    .reduce(
      (result, currentNumber, currentIndex) =>
         currentIndex % 2
          ? result + +currentNumber
          : result
    , 0);

// Longer answers checks that the input value is correct...
const sumOfEveryOther = number => {
  if (!Number.isFinite(number)) {
    throw new Error('Passed value not a finite number');
  }

  // .. and double checks that the match does not return null.
  return (number.toString().match(/\d/g) || [])
    .reduce(
      (result, currentNumber, currentIndex) =>
         currentIndex % 2
          ? result + +currentNumber
          : result
    , 0)
}

// sumOfEveryOther(123456789) // 20
// sumOfEveryOther(10) // 0
// sumOfEveryOther(1010.11) // 1