Benchmark: Adding to an existing array from another (loop, for of, forEach, spread) [1]

Script Preparation code:

window.testData = [];
populateTestData();
window.tempData = window.testData.slice();

function populateTestData() {
  for (let i = 0; i < 100; i++) {
    const newValue = Math.random();
    window.testData.push(newValue);
  }
}

function resetData() {
  window.testData.length = 0;
  window.tempData.length = 0;
}

function testForI() {
  for (let i = 0; i < window.testData.length; i++) {
    window.tempData.push(window.testData[i]);
  }
}

function testForOf() {
  for (const item of window.testData) {
    window.tempData.push(item);
  }
}

function testSpread() {
  window.tempData.push(...window.testData);
}

function testForEach() {
  window.testData.forEach((i) => window.tempData.push(i));
}

function testSlice() {
  window.tempData = window.testData.slice();
}

Tests:

For I
resetData() populateTestData() testForI();
For Of
resetData() populateTestData() testForOf();
Spread
resetData() populateTestData() testSpread();
ForEach
resetData() populateTestData() testForEach();
Slice
resetData() populateTestData() testSlice();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For I
For Of
Spread
ForEach
Slice

Fastest: N/A

Slowest: N/A

ⓘ Get performance results from real users on your website with Request Metrics.

Website Performance Monitoring by Request Metrics

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:107.0) Gecko/20100101 Firefox/107.0

Browser/OS: Firefox 107 on Windows

View result in a separate tab

Test name	Executions per second
For I	21814.3 Ops/sec
For Of	42828.0 Ops/sec
Spread	80300.6 Ops/sec
ForEach	41361.4 Ops/sec
Slice	81976.0 Ops/sec

Adding to an existing array from another (loop, for of, forEach, spread) [1] (version: 0)

Comparing performance of: For I vs For Of vs Spread vs ForEach vs Slice

Created: one year ago by: Guest

Jump to the latest result

For I

For Of

Spread

ForEach

Slice

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A