Benchmark: For vs map vs forEach vs for in

Script Preparation code:

var data = [1,2,3,4,5,6,7,8,9];

Tests:

for in loop
for (const d in data) { d + 1; }
map
data.map(d => d + 1);
forEach
data.forEach(d => d + 1);
for
for (let i = 0; i < data.length; i++) { data[i] + 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in loop
map
forEach
for

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down what is being tested on the provided JSON and explain the different approaches compared.

**Benchmark Definition**

The benchmark definition is a set of four JavaScript loops that iterate over an array `data` to increment each element by 1:

1. `for in`: This loop uses the `for...in` statement, which iterates over the properties (keys) of an object. In this case, it's used to iterate over the elements of the `data` array.
2. `map()`: This is a method on arrays that creates a new array with the results of applying a provided function to every element in the original array.
3. `forEach()`: This is another method on arrays that executes a callback function once for each element in the array.
4. `for`: This loop uses a traditional `for` loop with an index variable `i` to iterate over the elements of the `data` array.

**Options Compared**

The benchmark compares the performance of these four approaches:

1. **Traditional `for` loop**: Iterates using an explicit index variable.
2. **`for in` loop**: Iterates using the `for...in` statement, which iterates over object properties (keys).
3. **`map()`**: Creates a new array with transformed elements.
4. **`forEach()`**: Executes a callback function once per element.

**Pros and Cons**

Here's a brief summary of each approach:

1. **Traditional `for` loop**:
	* Pros: Easy to read, well-understood syntax.
	* Cons: Requires manual index management, can be error-prone if indexing is off.
2. **`for in` loop**:
	* Pros: Simple and concise, doesn't require explicit indexing.
	* Cons: Can be slower due to the overhead of iterating over object properties (keys).
3. **`map()`**:
	* Pros: Creates a new array with transformed elements, can be parallelized for better performance.
	* Cons: Requires an additional function call, creates a new array which may not be desirable for large datasets.
4. **`forEach()`**:
	* Pros: Simple and concise, doesn't require explicit indexing.
	* Cons: Executes the callback function synchronously, which can lead to slower performance compared to parallelizing `map()`.

**Library Used**

None explicitly mentioned in the provided JSON. However, it's likely that the benchmark uses a JavaScript runtime engine like V8 (used by Chrome) or SpiderMonkey (used by Firefox).

**Special JS Features/Syntax**

There are no special JS features or syntax used in this benchmark. The focus is on comparing different iteration approaches.

**Other Alternatives**

In addition to the four loops mentioned, other alternatives for iterating over arrays might include:

1. **`while` loop**: Another traditional looping construct.
2. **`for...of` loop**: A more modern looping construct that iterates over array elements using a `for...of` statement (not used in this benchmark).
3. **Parallel iteration libraries**: Libraries like `pmap` or `parallel-map` can be used to parallelize the execution of loops, potentially improving performance.

The choice of iteration approach depends on the specific use case and performance requirements.

Latest run results:

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

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/115.0.5790.160 Mobile/15E148 Safari/604.1

Browser/OS: Chrome Mobile iOS 115 on iOS 16.6

View result in a separate tab

Test name	Executions per second
for in loop	3800148.2 Ops/sec
map	13461268.0 Ops/sec
forEach	19896042.0 Ops/sec
for	1894503.9 Ops/sec

Related benchmarks:

For vs map vs forEach vs for in (version: 1)

Which one is faster?

Comparing performance of: for in loop vs map vs forEach vs for

Created: one year ago by: Registered User

Jump to the latest result

for in loop

map

forEach

for

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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