Benchmark: Array filter vs. for loop - with for in vs for loop without reindexing

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 without reindexing
var newElements = arr.length; for (var i=0,len=arr.length;i<len;i++) { if (arr[i]<=4) { arr[i] = undefined; newElements -= 1; }; } farr = Array.from({length: newElements}); var added = 0; for (var i=0,len=arr.length;i<len;i++) { if (arr[i] !== undefined) { farr[added] = arr[i]; added++; } }
For in
for (var i in arr) { 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 without reindexing
For in

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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**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmark that compares four different approaches to filter an array:

1. `Array.filter()`
2. Traditional `for` loop
3. `for` loop with `in` keyword
4. Traditional `for` loop without reindexing (using `newElements` variable)

**What is being tested?**

The benchmark measures the execution time of each approach to filter an array containing 10 elements, where only elements greater than 4 are included in the resulting array.

**Options Compared**

Here's a brief overview of each option:

1. **Array.filter()**: This method uses the `filter()` function to create a new array with all elements that pass the test implemented by the provided function. In this case, the filter function checks if each element is greater than 4.
2. **Traditional `for` loop**: This approach uses a traditional `for` loop to iterate over the array and push elements greater than 4 into a new array (`farr`).
3. **`for` loop with `in` keyword**: In this variant, the `for...in` loop is used to iterate over the array elements, but instead of checking for elements greater than 4 directly, it checks if each element is greater than 4 and pushes those into the `farr` array.
4. **Traditional `for` loop without reindexing**: This approach uses a traditional `for` loop with an `i` variable to iterate over the array elements. If an element is not greater than 4, it sets the corresponding value in the original array to `undefined`, effectively skipping that element. Afterward, it creates a new array (`farr`) with only the remaining elements.

**Pros and Cons**

Here's a brief summary of each approach:

1. **Array.filter()**: Pros: concise, efficient, and easy to read. Cons: may incur overhead due to function invocation.
2. **Traditional `for` loop**: Pros: well-known, simple to understand, and can be optimized for specific use cases. Cons: more verbose than Array.prototype methods and may lead to errors if not implemented correctly.
3. **`for` loop with `in` keyword**: Pros: concise and readable. Cons: less intuitive than traditional `for` loops and may cause confusion due to the `in` keyword's usage.
4. **Traditional `for` loop without reindexing**: Pros: can be optimized for specific use cases, but it requires careful handling of array modifications. Cons: more complex implementation compared to Array.prototype methods or traditional `for` loops.

**Libraries and Features**

There are no libraries mentioned in the provided benchmark definition.

**Special JS Feature/Syntax**

None mentioned.

**Alternative Approaches**

Other approaches that could be used for filtering arrays include:

* Using `Array.prototype.forEach()` with a callback function
* Utilizing modern JavaScript features like arrow functions, destructuring, or rest parameters
* Leveraging libraries like Lodash or Ramda

These alternatives may offer performance benefits or simplification over the existing benchmark options. However, their adoption depends on the specific use case and personal preference.

Keep in mind that this is just a general overview of each approach, and actual implementation details might vary based on individual requirements and constraints.

Related benchmarks:

Array filter vs. for loop - with for in vs for loop without reindexing (version: 0)

Comparing performance of: Filter vs For vs For without reindexing vs For in

Created: 4 years ago by: Guest

Jump to the latest result

Filter

For

For without reindexing

For in

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):