Benchmark: javascript loops

Tests:

foreach
const items = Array.from({length: 1000}, () => Math.floor(Math.random() * 40)); let index = 0; items.forEach(i => index++);
for-in
const items = Array.from({length: 1000}, () => Math.floor(Math.random() * 40)); let index = 0; for (let i in items) { index++; }
for-of
const items = Array.from({length: 1000}, () => Math.floor(Math.random() * 40)); let index = 0; for (let i of items) { index++; }
for
const items = Array.from({length: 1000}, () => Math.floor(Math.random() * 40)); let index = 0; for(let i = 0; i < items.length; ++i) { index++; }
optimized-for
const items = Array.from({length: 1000}, () => Math.floor(Math.random() * 40)); let index = 0; for(let i = items.length; i > 0; --i) { index++; }

Historical Performance Data aggregated from 265 community runs

Desktop Results:

Chrome 186 runs

optimized-for

10K/s

for

9K/s

for-of

9K/s

foreach

9K/s

for-in

7K/s

Fastest: optimized-for (1.3x faster)

View exact numbers

✓ optimized-for: 9,539 ops/sec
• for: 9,450 ops/sec
• for-of: 9,084 ops/sec
• foreach: 8,893 ops/sec
• for-in: 7,341 ops/sec

Firefox 50 runs

for

89K/s

optimized-for

89K/s

for-of

59K/s

foreach

56K/s

for-in

13K/s

Fastest: for (7.0x faster)

View exact numbers

✓ for: 89,012 ops/sec
• optimized-for: 88,502 ops/sec
• for-of: 59,260 ops/sec
• foreach: 55,750 ops/sec
• for-in: 12,642 ops/sec

Safari 8 runs

foreach

224K/s

for

191K/s

optimized-for

187K/s

for-of

159K/s

for-in

25K/s

Fastest: foreach (8.9x faster)

View exact numbers

✓ foreach: 223,643 ops/sec
• for: 191,427 ops/sec
• optimized-for: 186,699 ops/sec
• for-of: 158,582 ops/sec
• for-in: 25,084 ops/sec

Mobile Results:

Chrome 15 runs

for-of

7K/s

for

7K/s

optimized-for

7K/s

foreach

7K/s

for-in

5K/s

Fastest: for-of (1.4x faster)

View exact numbers

✓ for-of: 6,979 ops/sec
• for: 6,770 ops/sec
• optimized-for: 6,624 ops/sec
• foreach: 6,570 ops/sec
• for-in: 5,160 ops/sec

Safari 6 runs

for

11K/s

for-of

11K/s

optimized-for

11K/s

foreach

10K/s

for-in

9K/s

Fastest: for (1.3x faster)

View exact numbers

✓ for: 11,500 ops/sec
• for-of: 11,427 ops/sec
• optimized-for: 11,368 ops/sec
• foreach: 9,639 ops/sec
• for-in: 8,609 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
foreach
for-in
for-of
for
optimized-for

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:153.0) Gecko/20100101 Firefox/153.0

Browser/OS: Firefox 153 on Linux

View result in a separate tab

for

91K/s

optimized-for

90K/s

for-of

72K/s

foreach

49K/s

for-in

17K/s

View exact numbers

Test name	Executions per second
✓ for	91,301 Ops/sec
optimized-for	90,026 Ops/sec
for-of	71,658 Ops/sec
foreach	49,248 Ops/sec
for-in	16,939 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its results.

**Benchmark Definition**

The benchmark is designed to test the performance of different JavaScript loop constructs: `forEach`, `for-in`, `for-of`, and traditional `for` loops, as well as an optimized version of the `for` loop. The benchmark measures the time taken by each loop construct to iterate over a large array of random numbers.

**Options Compared**

The benchmark compares four main options:

1. **`forEach`**: This method calls a provided callback function for each element in an array, without requiring explicit index management.
2. **`for-in`**: This loop construct iterates over the properties (including indices) of an object using the `in` operator.
3. **`for-of`**: This is a newer loop construct introduced in ECMAScript 2015, which allows iterating over arrays or iterators without requiring explicit index management.
4. **Traditional `for` loop**: This classic loop construct uses a counter variable to iterate over an array.

**Pros and Cons**

Here's a brief summary of the pros and cons of each option:

* **`forEach`**: Pros: concise, easy to read, and maintain. Cons: can be slower due to the overhead of function calls and potentially more memory allocations.
* **`for-in`**: Pros: works on both arrays and objects. Cons: can be slower due to the overhead of accessing properties using `in`, and may not work well with arrays that have a large number of numeric indices (which are assumed to be property names).
* **`for-of`**: Pros: concise, easy to read, and maintain. Cons: requires support for modern JavaScript versions; can be slower due to the overhead of creating an iterator.
* **Traditional `for` loop**: Pros: widely supported, fast, and flexible. Cons: may require more boilerplate code.

**Optimized `for` Loop**

The optimized version of the `for` loop uses a technique called "iterative increment" instead of incrementing the counter variable using the ++ operator. This optimization can reduce the overhead of incrementing the counter variable, potentially leading to faster performance.

**Libraries and Special Features**

In this benchmark, none of the test cases use any external libraries or special JavaScript features beyond what's included in the standard ECMAScript specification.

**Other Alternatives**

For more comprehensive loop performance comparisons, consider using other benchmarks like:

* jsPerf
* Benchmark.js
* Google's Closure Compiler

These tools provide a wider range of test cases and can offer more detailed insights into the performance characteristics of different JavaScript loops.

javascript loops (version: 1) Benchmark.js

Comparing performance of: `foreach vs for-in vs for-of vs for vs optimized-for`

Created: 6 years ago by: Registered User

Go to the latest result

foreach

for-in

for-of

for

optimized-for

Historical Performance Data aggregated from 265 community runs

Desktop Results:

Chrome 186 runs

Firefox 50 runs

Safari 8 runs

Mobile Results:

Chrome 15 runs

Safari 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

javascript loops (version: 1) Benchmark.js

Comparing performance of: foreach vs for-in vs for-of vs for vs optimized-for

Created: 6 years ago by: Registered User

Go to the latest result

foreach

for-in

for-of

for

optimized-for

Historical Performance Data aggregated from 265 community runs

Desktop Results:

Chrome 186 runs

Firefox 50 runs

Safari 8 runs

Mobile Results:

Chrome 15 runs

Safari 6 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: `foreach vs for-in vs for-of vs for vs optimized-for`