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

Script Preparation code:

var array = new Array(1000);

Tests:

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

Historical Performance Data aggregated from 17 community runs

Desktop Results:

Chrome 17 runs

for..in

1.2M/s

foreach

490K/s

some

478K/s

for

447K/s

for..of

130K/s

Fastest: for..in (9.3x faster)

View exact numbers

✓ for..in: 1,210,071 ops/sec
• foreach: 489,896 ops/sec
• some: 478,475 ops/sec
• for: 446,754 ops/sec
• for..of: 129,622 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
some
for..of
for..in

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Windows

View result in a separate tab

for..in

473K/s

foreach

335K/s

some

315K/s

for

220K/s

for..of

47K/s

View exact numbers

Test name	Executions per second
✓ for..in	472,841 Ops/sec
foreach	334,844 Ops/sec
some	315,153 Ops/sec
for	219,583 Ops/sec
for..of	46,981 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**What is tested?**

MeasureThat.net is testing the performance of four different loop types in JavaScript:

1. `for` loop
2. `forEach` method
3. `some` method
4. `for...of` loop (introduced in ECMAScript 2015)
5. `for...in` loop (introduced in ECMAScript 1999)

The test cases are designed to measure the performance of each loop type on a large array of 1000 elements.

**Options compared**

Each test case is comparing the performance of two or more loop types, resulting in multiple runs for each test. The options being compared include:

* `for` loop vs. `forEach` method
* `forEach` method vs. `some` method
* `some` method vs. `for...of` loop
* `for` loop vs. `for...of` loop
* `for` loop vs. `for...in` loop

**Pros and cons of each approach**

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

1. **`for` loop**:
	* Pros: Control over iteration, easy to implement, works well for small arrays.
	* Cons: Can be slower than other methods, may require more memory allocation.
2. **`forEach` method**:
	* Pros: Concise syntax, works well with array methods, efficient execution.
	* Cons: May not work as expected if array is modified during iteration.
3. **`some` method**:
	* Pros: Efficient and concise syntax, suitable for testing conditional logic.
	* Cons: May be slower than `for` loop or `forEach` method due to overhead of function invocation.
4. **`for...of` loop** (ECMAScript 2015):
	* Pros: More expressive syntax, efficient execution, works well with arrays and iterables.
	* Cons: Less control over iteration compared to traditional `for` loops.
5. **`for...in` loop** (ECMAScript 1999):
	* Pros: Works well with object properties, efficient execution.
	* Cons: May not be suitable for array-based operations due to property iteration.

**Library usage**

None of the test cases explicitly use any external libraries. However, `forEach` and `some` methods are built-in methods in JavaScript, which are part of the language standard.

**Special JS features or syntax**

There are no special JS features or syntax used in these test cases.

**Other alternatives**

Other loop types that could be tested include:

* `while` loops
* Array destructuring (e.g., using destructing assignment)
* Other array methods, such as `map`, `filter`, or `reduce`

However, these additional tests would require modifications to the benchmark setup and test cases.

**Benchmark preparation code**

The script preparation code creates an array of 1000 elements, which is a common use case for testing loop performance. The HTML preparation code is empty, indicating that no additional DOM-related work is performed before running the benchmarks.

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

Compare loop performance

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

Created: 4 years ago by: Guest

Go to the latest result

for

foreach

some

for..of

for..in

Historical Performance Data aggregated from 17 community runs

Desktop Results:

Chrome 17 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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

Compare loop performance

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

Created: 4 years ago by: Guest

Go to the latest result

for

foreach

some

for..of

for..in

Historical Performance Data aggregated from 17 community runs

Desktop Results:

Chrome 17 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 some vs for..of vs for..in`