js for loop speed test

var myarray = []
for (var i=0; i<5000000; i++) {
	myarray.push(i)
}

var time, newTime, wlen=0, wlength=0
for (var y=0; y<20; y++) {
  time = new Date()
  for (var x=0; x<10; x++) {
    for (var i=0; i<myarray.length; i++) {
    }
  }
  newTime = new Date()
  wlength += newTime - time
  
  time = new Date()
  for (var x=0; x<10; x++) {  
    for (var i=0, len=myarray.length; i<len; i++) {
    }
  }
  newTime = new Date()
  wlen += newTime - time
}

console.log('With var len: ' + (wlen/20))  
console.log('With .length: ' + (wlength/20))

results:

With var len: 195.65
With .length: 263.75