Run results for: for x of array & for k in object

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.87 Safari/537.36

Browser: Chrome 80

Operating system: Linux

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
for key in object	21.7 Ops/sec
for val of array	71.0 Ops/sec

Script Preparation code:

var obj = {}
var arr = [] 
for (var i = 0; i<100000; i++) {
   var val = Math.random()
   obj[i] = val
   arr[i] = val
}
var wtf
function loopObj () {
  for (var k in obj) {
    wtf = obj[k]
  }
}

function loopArr () {
  for (var val of arr) {
    wtf = val
  }
}

console.log('prepare=> obj =', obj, '; arr =', arr)

Tests:

for key in object
for (var k in obj) { wtf = obj[k] }
for val of array
for (var val of arr) { wtf = val }

Run results for: for x of array & for k in object

for key in object

for val of array