Most profit from stock quotes [solution] [JS]

first.js

const sum = (a, b) => a + b

const getMostProfitFromStockQuotes = (quotes, current = 0) => {
  if (quotes.length < 2) return current
  
  const max = Math.max(...quotes)
  
  const maxAt = quotes.indexOf(max)
  
  const left = quotes.slice(0, maxAt)
  const right = quotes.slice(maxAt + 1)
  
  const profitOnLeft = left
    .map(a => max - a)
    .reduce(sum, 0)  
  
  return getMostProfitFromStockQuotes(right, current + profitOnLeft)
}

second.js

const getMostProfitFromStockQuotes = (quotes) =>
  quotes.reduceRight(
    ([max, profit], next) =>
      next > max
        ? [next, profit]
        : [max, profit + max - next],
    [-Infinity, 0]
  )[1];