Benchmark: for vs foreach vs for..in vs for..of

Script Preparation code:

var array = new Array(100);

Tests:

for
for (var i = 0; i < array.length; i++) { array[i]; }
foreach
array.forEach(function(i) { array[i]; });
for in
for (var i in array) { array[i]; }
for..of
for (var i of array) { array[i]; }

Historical Performance Data aggregated from 395 community runs

Desktop Results:

Chrome 278 runs

for in

6.9M/s

foreach

6.5M/s

for..of

344K/s

for

223K/s

Fastest: for in (30.9x faster)

View exact numbers

✓ for in: 6,879,067 ops/sec
• foreach: 6,501,870 ops/sec
• for..of: 343,874 ops/sec
• for: 222,562 ops/sec

Firefox 72 runs

for in

89.6M/s

for

23.2M/s

foreach

11.0M/s

for..of

1.8M/s

Fastest: for in (48.8x faster)

View exact numbers

✓ for in: 89,614,672 ops/sec
• for: 23,169,310 ops/sec
• foreach: 11,021,742 ops/sec
• for..of: 1,836,774 ops/sec

Safari 14 runs

for

11.8M/s

for in

9.0M/s

foreach

634K/s

for..of

294K/s

Fastest: for (40.2x faster)

View exact numbers

✓ for: 11,828,104 ops/sec
• for in: 8,967,306 ops/sec
• foreach: 633,973 ops/sec
• for..of: 294,327 ops/sec

Mobile Results:

Chrome 16 runs

foreach

2.4M/s

for in

2.4M/s

for..of

87K/s

for

56K/s

Fastest: foreach (43.2x faster)

View exact numbers

✓ foreach: 2,417,881 ops/sec
• for in: 2,396,934 ops/sec
• for..of: 86,728 ops/sec
• for: 55,929 ops/sec

Safari 15 runs

for in

8.1M/s

foreach

593K/s

for

240K/s

for..of

212K/s

Fastest: for in (38.5x faster)

View exact numbers

✓ for in: 8,149,132 ops/sec
• foreach: 593,444 ops/sec
• for: 240,494 ops/sec
• for..of: 211,672 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
foreach
for in
for..of

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/152.0.0.0 Safari/537.36 Edg/152.0.0.0

Browser/OS: Chrome 152 on Mac OS X 10.15.7

View result in a separate tab

for in

10.3M/s

for..of

6.1M/s

foreach

5.4M/s

for

4.9M/s

View exact numbers

Test name	Executions per second
✓ for in	10,295,393 Ops/sec
for..of	6,051,471 Ops/sec
foreach	5,383,968 Ops/sec
for	4,896,224 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down what is being tested in the provided JSON benchmark.

**Benchmark Purpose:**
The goal of this benchmark is to compare the performance of different loop iteration methods: `for`, `foreach`, `for...in`, and `for...of`.

**Loop Iteration Methods Compared:**

1. **`for` Loop**: This is a traditional loop that uses an index variable (`i`) to iterate over the elements of an array.
2. **`forEach` Method**: This is a built-in method on arrays that allows you to execute a callback function for each element in the array.
3. **`for...in` Loop**: This loop iterates over the properties of an object (in this case, an array), including its indices.
4. **`for...of` Loop**: This is a newer loop iteration method introduced in ECMAScript 2015 (ES6) that allows you to iterate over the values of an array without using an index variable.

**Pros and Cons:**

* `for` Loop:
	+ Pros: Simple, easy to understand, and widely supported.
	+ Cons: Can be less efficient than other methods due to the need to manually manage the index variable.
* `forEach` Method:
	+ Pros: Concise and easy to read. No need to worry about index management.
	+ Cons: May not be as fast as other methods due to the overhead of a method call.
* `for...in` Loop:
	+ Pros: Can iterate over both indices and values, but note that it iterates over properties, not elements.
	+ Cons: Not ideal for iterating over arrays, as it may include non-enumerable properties. Also, its performance can be slower due to the additional overhead of accessing properties.
* `for...of` Loop:
	+ Pros: Newer and more modern method that allows for concise iteration without index management. It's also optimized for performance.
	+ Cons: May require newer JavaScript engines to execute.

**Library/Technology Used:**
None mentioned in the benchmark JSON, but it is likely that MeasureThat.net uses a browser emulator or a JavaScript engine like V8 (used by Chrome) to run the benchmarks.

**Special JS Features/Syntax:**
The `for...of` loop uses a new syntax introduced in ES6. If you're not familiar with it, don't worry! It's a relatively modern feature that allows for concise iteration over arrays without using an index variable.

**Alternatives:**
If you're interested in exploring other alternatives for loop iteration, here are some:

* `while` Loop: A traditional loop that uses a conditional statement to control the iteration.
* `do...while` Loop: Similar to a `while` loop but executes the loop body at least once before checking the condition.
* Array methods like `map()`, `filter()`, and `reduce()` can also be used for iteration, although they may have different use cases and performance characteristics.

I hope this explanation helps you understand what's being tested in the benchmark!

for vs foreach vs for..in vs for..of (version: 0) Benchmark.js

Compare loop performance

Comparing performance of: `for vs foreach vs for in vs for..of`

Created: 4 years ago by: Guest

Go to the latest result

for

foreach

for in

for..of

Historical Performance Data aggregated from 395 community runs

Desktop Results:

Chrome 278 runs

Firefox 72 runs

Safari 14 runs

Mobile Results:

Chrome 16 runs

Safari 15 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

for vs foreach vs for..in vs for..of (version: 0) Benchmark.js

Compare loop performance

Comparing performance of: for vs foreach vs for in vs for..of

Created: 4 years ago by: Guest

Go to the latest result

for

foreach

for in

for..of

Historical Performance Data aggregated from 395 community runs

Desktop Results:

Chrome 278 runs

Firefox 72 runs

Safari 14 runs

Mobile Results:

Chrome 16 runs

Safari 15 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `for vs foreach vs for in vs for..of`