Benchmark: Array filter vs. for loop (fixed)2

Script Preparation code:

var arr = [1,2,3,4,5,6,7,8,9,0], farr;

Tests:

Filter
farr = arr.filter(function(item) { return (item>4); } );
For
for (var i=0,len=arr.length;i<len;i++) { if (arr[i]<5) continue; farr.push(arr[i]); }
For 2
for (var i=0,len=arr.length;i<len;i++) { if (arr[i]>4) farr.push(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Filter
For
For 2

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down what is tested in this benchmark, and I'll explain the different options compared, their pros and cons, and other considerations.

**Benchmark Definition**

The benchmark measures the performance of two approaches to filter an array:

1. Using `Array.prototype.filter()`
2. Using a traditional `for` loop

The array `arr` is defined with 10 elements, including one element that is out of range (0), which will be ignored by both filters.

**Options Compared**

There are three test cases:

1. **Filter**: This uses the built-in `Array.prototype.filter()` method to create a new array containing only the elements that pass the condition (`item > 4`).
2. **For**: This uses a traditional `for` loop to iterate over the array and push elements into a new array (`farr`) if they meet the condition (`arr[i] < 5`).
3. **For 2**: This is similar to the previous `For` test case, but it checks for `arr[i] > 4` instead of `arr[i] < 5`.

**Pros and Cons**

* **Filter**: This approach is generally faster because it uses native JavaScript optimization. However:
	+ It requires a new array to be created, which can lead to memory overhead.
	+ The condition (`item > 4`) is evaluated for each element in the original array, which might be slower if the condition is expensive or unpredictable.
* **For**: This approach avoids creating a new array, but:
	+ It uses a loop, which can introduce overhead due to function calls and iteration management.
	+ The loop variable (`i`) needs to be manually updated on each iteration, which can lead to slightly slower performance compared to the built-in `filter()` method.

**Other Considerations**

* **Cache locality**: In the `For` tests, the array elements are accessed sequentially (by index), which can improve cache locality. This might give it a small performance boost.
* **Branch prediction**: The condition (`arr[i] < 5`) is evaluated for each element, and the branch predictor may make educated guesses about whether to execute the code path based on the element's value. This can lead to minor performance variations.

**Library Usage**

None of the test cases use any external libraries.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark. The tests only rely on standard JavaScript language and library features.

**Alternative Approaches**

Other approaches that could be tested include:

1. Using `Array.prototype.map()` instead of `filter()`
2. Using a regular expression to filter the array
3. Using a `Set` data structure to keep track of filtered elements
4. Comparing performance with different JavaScript engines (e.g., SpiderMonkey, V8)

However, these alternatives would likely require significant modifications to the benchmark definition and test cases to accurately measure their performance impact.

Related benchmarks:

Array filter vs. for loop (fixed)2 (version: 0)

Comparing performance of: Filter vs For vs For 2

Created: 5 years ago by: Guest

Jump to the latest result

Filter

For

For 2

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):