Run results for: Caching length property vs getting it each time in the loop

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:136.0) Gecko/20100101 Firefox/136.0

Browser: Firefox 136

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Cache length

1.8M/s

Do not cache

1.3M/s

View exact numbers

Test name	Executions per second
✓ Cache length	1,849,856 Ops/sec
Do not cache	1,261,023 Ops/sec

Script Preparation code:

var arr = [];
var count = 1000;
for(var i = 0; i<count; i++)
{
  arr.push(i);
}

Tests:

Cache length
var arrLen = arr.length; var sum = 0; for (var i = 0; i < arrLen; i++){ sum = arr[i]; }
Do not cache
var sum = 0; for (var i = 0; i < arr.length; i++){ sum = arr[i]; }