Evaluating 2 versions of a JavaScript `array.reduce`

reduceVersion1.js

const valueArrays = [
  [1, 2],
  [100, 400, 700],
]

const TOTAL_COMBINATIONS = valueArrays
  .reduce((accumulator, values, index) => {
    if (index === 0) {
      return values.length
    }
    return accumulator * values.length
  }, 0)

reduceVersion2.js

const valueArrays = [
  [1, 2],
  [100, 400, 700],
]

const TOTAL_COMBINATIONS = valueArrays
  .map(values => values.length)
  .reduce((accumulator, length) => (accumulatora * length))