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

Run details:

User agent: Mozilla/5.0 (Android 8.0.0; Mobile; rv:63.0) Gecko/63.0 Firefox/63.0

Browser: Firefox Mobile 63

Operating system: Android 8.0.0

Device Platform: Mobile

Date tested: 5 years ago

Test name	Executions per second
Cache length	30382.2 Ops/sec
Do not cache	15536.9 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]; }