for-loop vs. for-in-loop (v26)

Revision 26 of this benchmark created on

Description

Testing the speed of iterating various sized arrays with straight for-loop or with a for-in-loop over its keys.

Preparation HTML

<script>
  // setup `arr` array ('small')
  var arr = ['1', true, false, "", void 0, null, 2, 18.5936];
  
  // testing for having deleted keys in array
  delete(arr[3]);
  
  // seed `arr_keys` hash
  var arr_keys = {};
  for (var i = 0; i < arr.length; i++) {
   arr.hasOwnProperty(i) && (arr_keys[i] = 0);
  }
  
  // setup `arr2` array ('medium')
  var arr2 = arr.slice(0);
  for (var j = 0; j < 500; j++) {
   arr2.push(Math.round(Math.random()));
  }
  
  // seed `arr2_keys` hash
  var arr2_keys = {};
  for (j = 0; j < arr2.length; j++) {
   arr2.hasOwnProperty(j) && (arr2_keys[j] = 0);
  }
  
  // setup `arr3` array ('big')
  var arr3 = arr2.slice(0);
  for (var m = 0; m < 5000; m++) {
   arr3.push(Math.round(Math.random()));
  }
  
  // seed `arr3_keys` hash
  var arr3_keys = {};
  for (m = 0; m < arr3.length; m++) {
   arr3.hasOwnProperty(m) && (arr3_keys[m] = 0);
  }
</script>

Test runner

Ready to run.

Testing in
TestOps/sec
small array: for-loop
for (var i=0; i<10000; i++) {
for (var i = 0, len = arr.length; i < len; i++) {
  if (i === 0) {
    arr[i] + 1;
  } else {
    arr[i];
  }
}
}
ready
small array: for-loop with pre
for (var i=0; i<10000; i++) {
if (arr.length > 0) {
  arr[0] + 1;
}
for (var i = 1, len = arr.length; i < len; i++) {
  arr[i];
}
}
ready
medium array: for-loop
for (var i=0; i<10000; i++) {
for (var i = 0, len = arr2.length; i < len; i++) {
  if (i === 0) {
    arr2[i] + 1;
  } else {
    arr2[i];
  }
}
}
ready
medium array: for-loop with pre
for (var i=0; i<10000; i++) {
if (arr2.length > 0) {
  arr2[0] + 1;
}
for (var i = 1, len = arr2.length; i < len; i++) {
  arr2[i];
}
}
ready
big array: for-loop
for (var i=0; i<10000; i++) {
for (var i = 0, len = arr3.length; i < len; i++) {
  if (i === 0) {
    arr3[i] + 1;
  } else {
    arr3[i];
  }
}
}
ready
big array: for-loop with pre
for (var i=0; i<10000; i++) {
if (arr3.length > 0) {
  arr3[0] + 1;
}
for (var i = 1, len = arr3.length; i < len; i++) {
  arr3[i];
}
}
ready

Revisions

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