Benchmark: for vs foreach vs some vs for..of vs for cached

Script Preparation code:

var array = new Array(100);

Tests:

for
for (let i = 0; i < array.length; i++) { array[i] = i % 2; }
foreach
array.forEach(i => { array[i] = i % 2; });
some
array.some(i => { array[i] = i % 2; });
for..of
for (const i of array) { array[i] = i % 2; }
for cached
for (let i = 0, l = array.length; i < l; i++) { array[i] = i % 2; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
foreach
some
for..of
for cached

Fastest: N/A

Slowest: N/A

Latest run results:

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

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I'll provide a detailed explanation of the benchmark, its test cases, and the different approaches compared.

**Benchmark Overview**

The benchmark aims to compare the performance of different loop constructs in JavaScript: `for`, `foreach`, `some`, and `for..of` with caching. The goal is to identify which approach is the most efficient.

**Test Cases**

Each test case represents a specific loop construct:

1. **`for`**: A traditional `for` loop that iterates over an array using a counter variable.
2. **`foreach`**: A loop that uses the `forEach` method, which executes a callback function for each element in the array.
3. **`some`**: A loop that uses the `some` method, which returns a boolean value indicating whether at least one element in the array passes a test.
4. **`for..of`**: A loop that uses the `for..of` statement, which iterates over an iterable (in this case, an array) using a foreach-like syntax.
5. **`for cached`**: A loop that uses a traditional `for` loop with caching, where the counter variable is stored in a separate variable to avoid recalculating it on each iteration.

**Performance Comparison**

The benchmark measures the execution time of each test case on a Chrome 80 browser running on Windows 10. The results are as follows:

* **`for cached`**: 155,528.5625 executions per second
* **`some`**: 152,049.984375 executions per second
* **`foreach`**: 149,964.078125 executions per second
* **`for..of`**: 149,718.109375 executions per second
* **`for`**: 77,041.2265625 executions per second

The results indicate that:

* `for cached` is the fastest approach.
* `some` and `foreach` are very close in performance, with `foreach` being slightly faster.
* `for..of` is slower than both `foreach` and `some`.
* `for` is the slowest approach.

**Pros and Cons**

Here's a brief summary of each approach:

1. **`for cached`**: Pros: avoids recalculating the counter variable on each iteration, which can improve performance. Cons: requires manual caching.
2. **`foreach`**: Pros: concise and easy to read, with good cache locality. Cons: may have slower performance due to method call overhead.
3. **`some`**: Pros: concise and easy to read, with good cache locality. Cons: may have slower performance due to method call overhead.
4. **`for..of`**: Pros: concise and easy to read, with good cache locality. Cons: slower than traditional `foreach` or `some`.
5. **`for`**: Pros: widely supported and well-understood. Cons: slower performance compared to other approaches.

**Other Considerations**

* The benchmark assumes that the array is large enough to benefit from caching. If the array is small, the difference in performance between approaches may be negligible.
* The `for cached` approach relies on caching the counter variable, which can lead to incorrect results if the cache is not properly implemented.
* The `foreach` and `some` methods have additional overhead due to method call and object lookup, which may affect their performance.

**Alternatives**

If you're looking for alternative loop constructs or optimization techniques, consider:

1. **`Map.prototype.forEach()`**: A more efficient alternative to `forEach`, as it avoids the overhead of a separate array.
2. **`Array.prototype.reduce()`**: A concise way to iterate over an array and accumulate values.
3. **`Set` or `Map` data structures**: For efficient set operations, such as union, intersection, or difference.

Keep in mind that the choice of loop construct ultimately depends on the specific use case and performance requirements.

Related benchmarks:

for vs foreach vs some vs for..of vs for cached (version: 0)

Compare loop performance

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

Created: 6 years ago by: Guest

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for

foreach

some

for..of

for cached

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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