Run results for: Variable declaration inside or outside for loop (less data 2)

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:74.0) Gecko/20100101 Firefox/74.0

Browser: Firefox 74

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
declaration inside for loop	0.7 Ops/sec
declaration outside for loop	0.7 Ops/sec

Script Preparation code:

function getRandomInt(max) {
  return Math.floor(Math.random() * Math.floor(max));
}

var data = [];
for(var i = 0; i < 1000; i++){
  data.push({value:getRandomInt(100)});
}

Tests:

declaration inside for loop
for (let i = 0; i < 1000; i++) { let array1 = []; let array2 = []; let array3 = []; array1.push(... data.filter(n => n > 50).map(n => n + 1)); array2.push(... data.filter(n => n > 50).map(n => n + 1)); array3.push(... data.filter(n => n > 50).map(n => n + 1)); }
declaration outside for loop
let array1 = []; let array2 = []; let array3 = []; for (let i = 0; i < 1000; i++) { array1 = []; array2 = []; array3 = []; array1.push(... data.filter(n => n > 50).map(n => n + 1)); array2.push(... data.filter(n => n > 50).map(n => n + 1)); array3.push(... data.filter(n => n > 50).map(n => n + 1)); }

Run results for: Variable declaration inside or outside for loop (less data 2)

declaration inside for loop

declaration outside for loop