Kinda related, but something different.
You should reference the array you are looping through in the reduce method (or any other functional loop). Et voila, your loop is quicker. Don't even use the reference.
Examples:
// this one is quicker...
sum = data.reduce((acc, curr, i, arr) => {
return acc + curr * curr
})
// than this one
sum = data.reduce((acc, curr) => {
return acc + curr * curr
})
(am using Node 8)