Benchmark: Array filter vs. for loop and for in

Script Preparation code:

var arr = [1,2,3,4,null,5,6,"7",8,{a:2},0], farr=[], i,len;

Tests:

Filter
farr= arr.filter(function(item) { return (item); });
For
farr = []; for (i=0,len=arr.length;i<len;i++) { farr.push(arr[i]); }
For in
farr = []; for(i in arr) { farr.push(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Filter
For
For in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:138.0) Gecko/20100101 Firefox/138.0

Browser/OS: Firefox 138 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Filter	20780782.0 Ops/sec
For	19695168.0 Ops/sec
For in	2731735.2 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into the benchmark results.

**What is being tested?**

The benchmark tests the performance of three different methods for filtering an array:

1. Using the `filter()` method (ECMAScript 5)
2. Using a traditional `for` loop
3. Using a `for...in` loop

**Options compared:**

We're comparing three approaches to filtering an array:

1. **Filter() method**: The `filter()` method is a built-in JavaScript function that creates a new array with all elements that pass the test implemented by the provided function.
2. **For loop**: A traditional `for` loop iterates over an array, and we're using it to create a new array with filtered elements.
3. **For...in loop**: The `for...in` loop is used to iterate over an object's enumerable properties. However, in this case, we're using it to iterate over the array indices.

**Pros and cons of each approach:**

1. **Filter() method**:
	* Pros: Concise code, easy to read, and well-suited for modern JavaScript development.
	* Cons: Might be slower than traditional loops due to function call overhead.
2. **For loop**:
	* Pros: Often faster than `filter()` since it avoids function calls.
	* Cons: More verbose code, potentially harder to read.
3. **For...in loop**:
	* Pros: Can be faster than traditional `for` loops when dealing with sparse arrays (arrays containing gaps in the indices).
	* Cons: Can lead to unexpected behavior if not used carefully, as it iterates over an array's properties rather than its indices.

**Other considerations:**

1. **Library usage**: There are no external libraries being used in these benchmarks.
2. **Special JavaScript feature or syntax**: The `filter()` method is a built-in ECMAScript 5 feature, which means it might not be supported in older browsers.
3. **Alternatives**: Other alternatives for filtering arrays include using the `some()` and `every()` methods or a combination of `forEach()` and conditional statements.

**Test case explanations:**

1. The first test case uses the `filter()` method to create a new array with all elements that are truthy (i.e., not null or undefined).
2. The second test case uses a traditional `for` loop to achieve the same result.
3. The third test case uses a `for...in` loop, which is generally discouraged when iterating over arrays.

**Benchmark results:**

The benchmark results show that the `filter()` method performs best on this particular task, followed by the `for` loop, and then the `for...in` loop. However, please note that these results are specific to the test environment and might vary depending on your system configuration and browser.

Related benchmarks:

Array filter vs. for loop and for in (version: 0)

This version declares i once before

Comparing performance of: Filter vs For vs For in

Created: 7 years ago by: Guest

Jump to the latest result

Filter

For

For in

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):