For example,

for (var i = 0; i < 3; i++) {
  setTimeout(function() {
    console.log(i)
  }, 500);

  let j = i;
  setTimeout(function() {
    console.log(j);
  }, 1000)
}

The event loop loupe result: 3 0 3 1 3 2

But in jsfiddle result: 3 3 3 0 1 2

I dont know what cause the two different results and which one would be the correct one.