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:56.0) Gecko/20100101 Firefox/56.0.1 Waterfox/56.0.1

Browser: Firefox 56

Operating system: Windows 7

Device Platform: Other

Date tested: 2025 years ago

Test name	Executions per second
Cache length	617869.0 Ops/sec
Do not cache	361687.6 Ops/sec

Script Preparation code:

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

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

Tests:

var arrLen = arr.length;
var sum = 0;
for (var i = 0; i < arrLen; i++){
  sum = arr[i];
}

 
var arrLen = arr.length;var sum = 0;for (var i = 0; i < arrLen; i++){  sum = arr[i];}

var sum = 0;
for (var i = 0; i < arr.length; i++){
  sum = arr[i];
}

 
var sum = 0;for (var i = 0; i < arr.length; i++){  sum = arr[i];}