Benchmark: for vs for in vs for each vs for of

Tests:

for

const arr = [1,2,3,4,5,6,7,8,9,10];
for (var i = 0; i < arr.length; i++){
	var number = arr[i];
}

AخA
 
const arr = [1,2,3,4,5,6,7,8,9,10];for (var i = 0; i < arr.length; i++){    var number = arr[i];}

for of

const arr = [1,2,3,4,5,6,7,8,9,10];
for (var n of arr){
  var number = n;
}

 
const arr = [1,2,3,4,5,6,7,8,9,10];for (var n of arr){  var number = n;}

for in

const arr = [1,2,3,4,5,6,7,8,9,10];
for (var i in arr){
	var number = arr[i];
}

 
const arr = [1,2,3,4,5,6,7,8,9,10];for (var i in arr){    var number = arr[i];}

forEach

const arr = [1,2,3,4,5,6,7,8,9,10];
arr.forEach(n => {
  var number = n;
});

 
const arr = [1,2,3,4,5,6,7,8,9,10];arr.forEach(n => {  var number = n;});

for 2

const arr = [1,2,3,4,5,6,7,8,9,10];
for (var i = 0, n = arr.length; i < n; i++){
	var number = arr[i];
}

 
const arr = [1,2,3,4,5,6,7,8,9,10];for (var i = 0, n = arr.length; i < n; i++){    var number = arr[i];}

while with shift
const arr = [1,2,3,4,5,6,7,8,9,10]; while(arr.length) { var number = arr.shift(); }
const arr = [1,2,3,4,5,6,7,8,9,10];
while(arr.length) {
var number = arr.shift();
}

while

const arr = [1,2,3,4,5,6,7,8,9,10];
var i = 0;
var n = arr.length;
while(i < n) {
	var number = arr[i];
  	++i;
}

 
const arr = [1,2,3,4,5,6,7,8,9,10];var i = 0;var n = arr.length;while(i < n) {    var number = arr[i];    ++i;}

while with length reduction
const arr = [1,2,3,4,5,6,7,8,9,10]; var len = arr.length; while (len--) { var number = arr[len]; }
const arr = [1,2,3,4,5,6,7,8,9,10];
var len = arr.length;
while (len--) {
var number = arr[len];
}

for reverse

const arr = [1,2,3,4,5,6,7,8,9,10];
for (var i = arr.length; i >= 0; --i){
	var number = arr[i];
}

 
const arr = [1,2,3,4,5,6,7,8,9,10];for (var i = arr.length; i >= 0; --i){    var number = arr[i];}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Experimental features:

Memory measurements supported only in Chrome.
For precise memory measurements Chrome must be launched with --enable-precise-memory-info flag.
More information: Monitoring JavaScript Memory

Test case name	Result
for
for of
for in
forEach
for 2
while with shift
while
while with length reduction
for reverse

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36

Browser/OS: Chrome 127 on Windows

View result in a separate tab

Test name	Executions per second
for	19339656.0 Ops/sec
for of	22831210.0 Ops/sec
for in	816927.6 Ops/sec
forEach	25731544.0 Ops/sec
for 2	25599286.0 Ops/sec
while with shift	2010041.9 Ops/sec
while	27336246.0 Ops/sec
while with length reduction	20193752.0 Ops/sec
for reverse	23216702.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 5 months ago):

Let's break down the provided benchmark and explain what's being tested.

Benchmark Overview

The benchmark compares the performance of six different loop constructs: for, for in, for each (also known as forEach), for 2, while with shift, and while. The test case uses an array of numbers to demonstrate the difference between these loops.

Options being compared

Here's a brief description of each option:

For: This is a traditional loop construct that iterates over an array using an index variable.
For in: This loop constructs iterate over the properties of an object (in this case, the array). It uses the property name as the iteration variable.
**For each` (forEach): This loop construct iterates over an array using a closure, where the callback function receives the current element and its index.
For 2: This is a variation of the traditional for loop that initializes the index variable twice, once before and once inside the loop.
While with shift: This loop constructs use a while loop and remove elements from the array using shift() to iterate over it.
**For in`: This loop construct iterates over the properties of an object (in this case, the array). It uses the property name as the iteration variable.

Performance Comparison

The benchmark measures the number of executions per second for each loop construct on a desktop system running Chrome 127. The results show that:

For and For in are the slowest loops, likely due to the overhead of accessing array elements using indices or property names.
For each (forEach) is relatively fast, as it uses a closure to iterate over the array, which is optimized by modern JavaScript engines.
For 2 is slightly faster than traditional for, but still slower than forEach.
While with shift is surprisingly slow, likely due to the overhead of removing elements from the array using shift().
While with length reduction is significantly faster than the other loops, as it avoids the overhead of accessing array elements and uses a simpler iteration logic.

Conclusion

This benchmark highlights the importance of choosing the right loop construct for your specific use case. For each (forEach) is often the best choice when you need to iterate over an array, while traditional for or while with shift might be better suited for other scenarios. The results also demonstrate the performance benefits of avoiding unnecessary overhead and using optimized iteration logic.

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares the performance of six different loop constructs: `for`, `for in`, `for each` (also known as `forEach`), `for 2`, `while with shift`, and `while`. The test case uses an array of numbers to demonstrate the difference between these loops.

**Options being compared**

Here's a brief description of each option:

1. **For**: This is a traditional loop construct that iterates over an array using an index variable.
2. **For in**: This loop constructs iterate over the properties of an object (in this case, the array). It uses the property name as the iteration variable.
3. **For each` (forEach): This loop construct iterates over an array using a closure, where the callback function receives the current element and its index.
4. **For 2**: This is a variation of the traditional `for` loop that initializes the index variable twice, once before and once inside the loop.
5. **While with shift**: This loop constructs use a while loop and remove elements from the array using `shift()` to iterate over it.
6. **For in`: This loop construct iterates over the properties of an object (in this case, the array). It uses the property name as the iteration variable.

**Performance Comparison**

The benchmark measures the number of executions per second for each loop construct on a desktop system running Chrome 127. The results show that:

* `For` and `For in` are the slowest loops, likely due to the overhead of accessing array elements using indices or property names.
* `For each` (forEach) is relatively fast, as it uses a closure to iterate over the array, which is optimized by modern JavaScript engines.
* `For 2` is slightly faster than traditional `for`, but still slower than `forEach`.
* `While with shift` is surprisingly slow, likely due to the overhead of removing elements from the array using `shift()`.
* `While with length reduction` is significantly faster than the other loops, as it avoids the overhead of accessing array elements and uses a simpler iteration logic.

**Conclusion**

This benchmark highlights the importance of choosing the right loop construct for your specific use case. `For each` (forEach) is often the best choice when you need to iterate over an array, while traditional `for` or `while with shift` might be better suited for other scenarios. The results also demonstrate the performance benefits of avoiding unnecessary overhead and using optimized iteration logic.

Related benchmarks:

for vs for in vs for each vs for of (version: 7)

Comparing performance of: for vs for of vs for in vs forEach vs for 2 vs while with shift vs while vs while with length reduction vs for reverse

Created: 5 years ago by: Registered User

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for