Benchmark: For vs Foreach copying an array

Script Preparation code:

var arr = [];
for (var i = 0; i < 1000000; i++) {
    arr[i] = i % 1000
}

Tests:

For
const countObj = {} for (let i = 0; i < arr.length; i++) { const value = arr[i] countObj[value] = (countObj[value] || 0) + 1 }
Foreach
const countObj = {} arr.forEach(value => { countObj[value] = (countObj[value] || 0) + 1 })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For
Foreach

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 dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The benchmark measures the performance of two approaches: `For` and `Foreach`. The script preparation code creates an array `arr` with 1 million elements, where each element is assigned a unique value (remainder of `i` divided by 1000). The goal is to count the occurrences of each value in the array.

**Options Compared**

The two approaches compared are:

1. **For Loop**: Iterates over the array using a traditional `for` loop.
2. **Foreach Loop**: Uses the `forEach` method to iterate over the array.

**Pros and Cons**

* **For Loop**:
	+ Pros: Can be more intuitive for some developers, as it uses a familiar syntax.
	+ Cons: May be slower due to the need to manage the loop variable (`i`) and increment it manually.
* **Foreach Loop**:
	+ Pros: Often faster, as it eliminates the need to manage the loop variable and increment it manually. It also allows for more concise code.
	+ Cons: Requires familiarity with the `forEach` method, which might be less common among developers.

**Library Used**

In both test cases, no specific library is used beyond what's built into JavaScript (e.g., the `Array.prototype.forEach` method). However, it's worth noting that some libraries or frameworks might provide optimized implementations of these loops, potentially affecting performance.

**Special JS Feature/Syntax**

Neither of the test cases uses any special JavaScript features or syntax beyond what's standard. The `forEach` method is a part of the ECMAScript specification and has been supported by most browsers since its introduction.

**Other Considerations**

When comparing loop performance, other factors can influence results, such as:

* Cache performance: Modern browsers have various caching mechanisms that can impact loop performance.
* Compiler optimizations: Some browsers or compilers might apply optimizations that affect loop performance.
* System resources: The availability of system resources like CPU, memory, and I/O bandwidth can impact the performance of the loops.

**Other Alternatives**

If you're interested in exploring other alternatives for this benchmark, you could consider using:

* Other iteration methods, such as `map()`, `filter()`, or `reduce()`.
* Different programming languages or frameworks that provide optimized loop implementations.
* Online tools or benchmarks that compare performance across various libraries or frameworks.

Keep in mind that the choice of alternative will depend on your specific use case and requirements.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:94.0) Gecko/20100101 Firefox/94.0

Browser/OS: Firefox 94 on Windows

View result in a separate tab

Test name	Executions per second
For	144.3 Ops/sec
Foreach	109.1 Ops/sec

Related benchmarks:

For vs Foreach copying an array (version: 0)

Testing performance getting and setting an object outside of the for loop scope

Comparing performance of: For vs Foreach

Created: 2 years ago by: Guest

Jump to the latest result

For

Foreach

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):