Benchmark: Array.forEch vs Array.filter

Script Preparation code:


window.arr = [];
for(let i = 0; i < 9999; i++) {
  arr.push(Date.now())
}

function cb(v) {
 console.log(v) 
}

Tests:

foreach if
window.arr.forEach((v) => { if (v % 2) { cb(v) } })
filter foreach
window.arr.filter((v) => v % 2).forEach((v) => cb(v))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach if
filter foreach

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 12 days ago)

User agent: Mozilla/5.0 (Linux; Android 13; Jelly Star Build/TP1A.220624.014; ) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Mobile Safari/537.36 EdgA/124.0.2478.64

Browser/OS: Chrome Mobile 124 on Android

View result in a separate tab

Test name	Executions per second
foreach if	7.7 Ops/sec
filter foreach	7.9 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 12 days ago):

LLMs can make mistakes. Check important info.

The benchmark provided compares two different approaches for processing arrays in JavaScript: using `Array.forEach` with an `if` condition and using `Array.filter` in conjunction with `Array.forEach`.

### Benchmark Overview

1. **Test Cases**:
   - **forEach with an if statement**: 
     ```javascript
     window.arr.forEach((v) => {
       if (v % 2) { cb(v) }
     });
     ```
     This test iterates through all elements in `window.arr` and executes the `cb` function for each element that is odd (i.e., when the value of `v` modulo 2 is true).
   
   - **Filter followed by forEach**: 
     ```javascript
     window.arr.filter((v) => v % 2).forEach((v) => cb(v));
     ```
     This first filters the array to obtain only the odd values and then applies the `cb` function to each of those filtered values.

2. **Definitions**:
   - `cb(v)`: A callback function defined in the preparation code that logs the value `v` to the console. This function is intentionally simple and serves as a placeholder to represent any action taken on the processed elements.

### Comparison of Approaches

#### **forEach with if statement**
- **Pros**:
  - **Simplicity**: The approach is straightforward, directly applying the condition to each element in a single pass.
  - **Memory Efficiency**: It does not create a new array, meaning less memory overhead.
  
- **Cons**:
  - **Unoptimized**: Every element is evaluated within the loop, using `if` on each iteration which can be slightly slower if the array is large.

#### **Filter followed by forEach**
- **Pros**:
  - **Readability**: The intent is clear; it separates the concerns of filtering and processing, which could be easier to understand.
  - **Functional Approach**: It leverages functional programming practices by processing data in a more declarative manner.
  
- **Cons**:
  - **Performance Overhead**: This involves two operations: filtering and then mapping the results, which can increase execution time, especially with larger arrays.
  - **Memory Usage**: A new array is created during the filtering process, leading to greater memory consumption.

### Considerations and Alternatives

- **Performance**: The execution speed (expressed in `ExecutionsPerSecond`) for filtering via `filter` combined with `forEach` was slightly better than the direct `forEach` with an `if` condition in this benchmark, but performance can vary based on the nature and size of the data.
- **Readability vs. Performance**: Depending on the need—be it clean code or high performance—developers might choose one method over the other. However, the best approach often depends on the specific use case.
  
### Other Alternatives
1. **Using a traditional for loop**: Using a `for` loop may yield the best performance for large datasets, as it allows explicit control over the iteration.
2. **Reducing calls**: For large arrays or performance-critical sections, using a single pass with a `for` loop that conditionally checks and processes values can be more efficient.
3. **Using `map` and `filter`**: For scenarios where you may want to transform data as you filter it, combining `map` and `filter` can provide both functionality and readability but at the cost of performance due to the creation of intermediate arrays.

In summary, both methods have their use case, trade-offs, and potential performance implications based on the data being processed and the computational context. Understanding these nuances is crucial for any software engineer aiming to write efficient JavaScript code.

Related benchmarks:

Array.forEch vs Array.filter (version: 1)

Comparing performance of: foreach if vs filter foreach

Created: 12 days ago by: Guest

Jump to the latest result

foreach if

filter foreach

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 12 days ago):