mesureFps.js

let i = 0
const t = Date.now() + 5000

function raf() {
  requestAnimationFrame(() => {
    if(Date.now() < t){
      i++
      // console.log(i) // console.log is very heavy!
      raf()
    }else{
      console.log('Frame rate is: %f fps', i / 5)
    }
  })
}

raf()
console.log('Testing frame rate...')