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

Run details:

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0

Browser: Firefox 57

Operating system: Windows 7

Device Platform: Other

Date tested: 2024 years ago

Test name	Executions per second
Cache length	202681.0 Ops/sec
Do not cache	123297.2 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]; }