instanceof is slow

instanceof-perf-test.js

(function() {
  'use strict'
  let s = fetch('/')

  console.time('t0')
  for (let i = 0; i < 1e9; i++) {
    if (true) {}
  }
  console.timeEnd('t0')


  console.time('typeof')
  for (let i = 0; i < 1e9; i++) {
    if (typeof s.then === 'function') {}
  }
  console.timeEnd('typeof')


  console.time('bool')
  for (let i = 0; i < 1e9; i++) {
    if (!!s.then) {
    }
  }
  console.timeEnd('bool')


  console.time('instanceof')
  for (let i = 0; i < 1e9; i++) {
    if (s instanceof Promise) {}
  }
  console.timeEnd('instanceof')
})()

t0: 846.892822265625 ms
typeof: 862.230224609375 ms
bool: 957.297119140625 ms
instanceof: 2862.81787109375 ms