second max compare

res.txt

Length of random ints array: 1000000
Run looper
res: 99999883
Time elapsed: 7
Run reducer
res: 99999883
Time elapsed: 26
Diff: 19

script.js

const arr = [...new Array(1000000)].map(() => Math.round(Math.random() * 100000000))
console.log('Length of random ints array:', arr.length)

function looper() {
  let max = Number.MIN_VALUE;
  let premax = Number.MIN_VALUE;
  let len = arr.length;
  for (let i = 0; i < len; i++) {
    let num = arr[i];
    if (num !== max) {
      if (num > max) {
        premax = max;
        max = num;
      } else if (num > premax) {
        premax = num;
      }
    }
  }
  return premax;
}

function reducer() {
  return arr.reduce((acc, v) => (acc[1] = acc[0] > v ? Math.max(acc[1], v) : acc[0], acc[0] = Math.max(acc[0], v), acc), [Number.MIN_VALUE, Number.MIN_VALUE])[1]
}

console.log('Run looper')
const lst = Date.now()
console.log('res:', looper())
const lfn = Date.now();
console.log('Time elapsed:', lfn - lst)
console.log('Run reducer')
const rst = Date.now()
console.log('res:', reducer())
const rfn = Date.now();
console.log('Time elapsed:', rfn - rst)
console.log('Diff:', (rfn - rst) - (lfn - lst))