Benchmark: indexOf + splice vs. filter

Script Preparation code:

var arr = new Array(15000);
arr.fill({ id: 0 });
arr = arr.map((el, idx) => el.id = idx);
var idToFilter = Math.floor(Math.random() * 15000);

Tests:

indexOf + splice
var index = arr.indexOf(idToFilter); var newArray = [...arr].splice(index, 1);
filter
var newArray = arr.filter(e => e.id !== idToFilter);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
indexOf + splice
filter

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 15 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
indexOf + splice	362006.1 Ops/sec
filter	19969.9 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 18 days ago):

LLMs can make mistakes. Check important info.

The benchmark provided compares two different approaches for removing an element from an array in JavaScript: using a combination of `indexOf` and `splice` versus using the `filter` method. Let's analyze both approaches:

### Benchmark Preparation Code

The benchmark preparation code creates an array of 15,000 objects where each object has an `id` property. The `id` is assigned a unique value based on its index in the array. A random `idToFilter` is then selected, representing the id of an element that will be removed from the array during the benchmark tests.

### Individual Test Cases

1. **Test Case 1: indexOf + splice**
   - **Benchmark Definition**: The first approach finds the index of the element to be removed using `indexOf()` and then creates a new array by using `splice()` to remove the element at that index.
   - **Execution**:
     ```javascript
     var index = arr.indexOf(idToFilter);
     var newArray = [...arr].splice(index, 1);
     ```
   - **Pros**:
     - Directly works with the index of the element, which makes it relatively straightforward for those familiar with working with indexes in arrays.
     - `splice` can also be used to modify the original array if needed.
   - **Cons**:
     - `indexOf` can have O(n) time complexity for searching the index, especially with larger arrays, meaning it takes longer for larger datasets.
     - `splice` creates a new array but modifies the original array's contents if not used with the spread operator. This can lead to unintentional mutations if developers aren’t careful.
   
2. **Test Case 2: filter**
   - **Benchmark Definition**: The second approach uses `filter()` to create a new array that excludes the element with the specified `id`.
   - **Execution**:
     ```javascript
     var newArray = arr.filter(e => e.id !== idToFilter);
     ```
   - **Pros**:
     - More declarative and concise. It clearly conveys the intent of filtering out unwanted elements.
     - Avoids mutation of the original array (unless the developer explicitly assigns it).
     - Generally performs better for larger arrays as it does not require separate index searching, although it does iterate through the array fully.
   - **Cons**:
     - For very large arrays and particularly when a large number of elements need to be filtered, the performance could degrade since it may have to traverse the entire array.

### Benchmark Results

The benchmark results indicate the performance of each test case:

- **indexOf + splice**: 164,226.38 executions per second
- **filter**: 21,455.07 executions per second

This results illustrate that `indexOf + splice` performs significantly better in this specific test scenario, likely due to the relatively small number of items in the array and the ability to quickly retrieve the index of the specified id.

### Other Alternatives

1. **Using `for` Loop**: Both methods can be alternatively written using traditional `for` loops where developers can manually push non-matching elements to a new array. This gives better control over the operation but makes the code longer and potentially more error-prone.

2. **Using `reduce`**: You could use the `reduce` method to build a new array without the unwanted element. Similar to `filter`, it reads all elements, but allows for more complex operations during array construction.

3. **Using a Set**: If the ids are unique and the operation needs frequent removals, keeping the original ids in a Set might allow O(1) lookups for filtering.

In conclusion, the choice between `indexOf + splice` and `filter` depends on the context of usage, array size, and whether or not mutation of the original array is acceptable in the application’s architecture. Each approach has its merits and trade-offs, making it crucial for software engineers to select the right method based on the scenarios they are facing.

Related benchmarks:

indexOf + splice vs. filter (version: 1)

Comparing performance of: indexOf + splice vs filter

Created: 18 days ago by: Guest

Jump to the latest result

indexOf + splice

filter

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 18 days ago):