Run results for: The fastest way to iterate over arrays

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:132.0) Gecko/20100101 Firefox/132.0

Browser: Firefox 132

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

for loop

49/s

for loop with length caching

38/s

forEach

10/s

for...of

8/s

map

4/s

for...in

1/s

View exact numbers

Script Preparation code:

var objectSize = 1000000;
var iterations = 20;

var array = [];

for (var i = 0; i < objectSize; i++) {
    array[i] = `val${i}`;
}

Tests:

for loop
for (var i = 0; i < iterations; i++) { for (var key = 0; key < array.length; key++) { var k = array[key]; } }
for loop with length caching
for (var i = 0; i < iterations; i++) { var length = array.length; for (var key = 0; key < length; key++) { var k = array[key]; } }
for...of
for (var i = 0; i < iterations; i++) { for (var value of array) { var k = value; } }
for...in
for (var i = 0; i < iterations; i++) { for (var key in array) { var k = array[key]; } }
forEach
for (var i = 0; i < iterations; i++) { array.forEach((value) => { var k = value; }); }
map
for (var i = 0; i < iterations; i++) { array.map((value) => { var k = value; }); }