Run results for: Compare Array.splice() and Array.copyWithin() to move item within an array

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:135.0) Gecko/20100101 Firefox/135.0

Browser: Firefox 135

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Move element by Array.copyWithin()

3.3M/s

Move element by Array.splice()

1.3M/s

View exact numbers

Test name	Executions per second
✓ Move element by Array.copyWithin()	3,308,300 Ops/sec
Move element by Array.splice()	1,336,597 Ops/sec

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

var data = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99]

function moveItemBySplice(from, to) {
  // remove `from` item and store it
  var f = data.splice(from, 1)[0];
  // insert stored item into position `to`
  data.splice(to, 0, f);
}

function moveItemByCopyWithin(from, to) {
  const f = data[from];
  if (to > from) {
    // copy items after `from` until `to` one index to the left
    data.copyWithin(from, from + 1, to + 1);
  } else {
    // copy items from `to` until before `from` one index to the right
    data.copyWithin(to + 1, to, from);
  }
  // insert stored item into position `to`
  data[to] = f;
}

Tests:

Move element by Array.splice()
moveItemBySplice(3, 40); moveItemBySplice(50, 10); moveItemBySplice(45, 96); moveItemBySplice(7, 15);
Move element by Array.copyWithin()
moveItemByCopyWithin(3, 40); moveItemByCopyWithin(50, 10); moveItemByCopyWithin(45, 96); moveItemByCopyWithin(7, 15);