Benchmark: Slice vs Splice vs Shift (Large Array 2)

Script Preparation code:

var array = Array(10000).fill(0)
var itemsToRemove = 5000

Tests:

array.slice()
array = array.slice(itemsToRemove)
array.splice()
array.splice(0, itemsToRemove)
array.shift()
for (let i = 0 ; i < itemsToRemove ; i++) array.shift()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array.slice()
array.splice()
array.shift()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 days ago)

User agent: Mozilla/5.0 (X11; CrOS x86_64 14695.114.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36

Browser/OS: Chrome 102 on Chrome OS 14695.114.0

View result in a separate tab

Test name	Executions per second
array.slice()	712342.2 Ops/sec
array.splice()	6672609.5 Ops/sec
array.shift()	17557.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 5 days ago):

LLMs can make mistakes. Check important info.

The benchmark provided is focused on comparing the performance of three different methods for removing items from the beginning of an array in JavaScript. The methods tested are `array.slice()`, `array.splice()`, and `array.shift()`. Each method has different characteristics, which are worth discussing for understanding their performance implications.

### Methods Compared

1. **`array.slice()`**:
   - **Benchmark Definition**: `array = array.slice(itemsToRemove)`
   - **Test Name**: "array.slice()"
   - **Functionality**: The `slice` method creates a new array containing a portion of the original array (in this case, the elements after the first `itemsToRemove` elements).
   - **Pros**:
     - Non-destructive: `slice` does not modify the original array; it returns a new array.
     - Clean syntax: The intention is clear, making the code readable.
   - **Cons**:
     - Performance impacts due to creation of a new array, which can be significant for large arrays, as the entire content is copied to a new reference.
   
2. **`array.splice()`**:
   - **Benchmark Definition**: `array.splice(0, itemsToRemove)`
   - **Test Name**: "array.splice()"
   - **Functionality**: The `splice` method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.
   - **Pros**:
     - Modifies the original array directly, potentially improving performance by avoiding the overhead of creating a new array.
     - Can be versatile as it can also be used to add new elements simultaneously.
   - **Cons**:
     - Destructive operation: Alters the original array, which may not be desirable in all contexts.
     - The shift of indexes for the remaining elements can add some performance overhead, but it's generally efficient for this context.

3. **`array.shift()`**:
   - **Benchmark Definition**: `for (let i = 0 ; i < itemsToRemove ; i++) array.shift()`
   - **Test Name**: "array.shift()"
   - **Functionality**: The `shift` method removes the first element from an array and returns that removed element. It alters the length of the array.
   - **Pros**:
     - Simple to use when needing to remove elements from the start of the array.
   - **Cons**:
     - Performance can be poor for large arrays as each call to `shift` re-indexes the remaining elements. This might lead to a higher time complexity (O(n) for each call), making it inefficient when removing many items (in this case, 5000).

### Benchmark Results

The results of the benchmark show the number of executions per second for each method:

- **array.splice()**: 37,893,508 executions per second (fastest method).
- **array.slice()**: 7,391,687.5 executions per second.
- **array.shift()**: 26,723.2890625 executions per second (slowest method).

### Considerations and Alternatives

- **When to Use Each Method**: 
  - Use `splice` when you need to modify the original array and focus on performance.
  - Use `slice` for cases where you need to maintain the original array and avoid side effects.
  - Avoid `shift` for large scale removals from the beginning of an array due to performance constraints.

- **Other Alternatives**:
  - **Using a Different Data Structure**: Depending on the requirements, consider using a Queue where elements can be added at one end and removed from the other end more efficiently (e.g., implemented using linked lists).
  - **Custom Implementations**: For complex scenarios, creating a custom function that combines benefits of these methods while managing performance and memory can be beneficial.

In summary, while testing array manipulations, understanding the underlying operations and efficiency trade-offs can guide engineers in choosing the right approach for their specific use cases. The benchmark illustrates clear distinctions in performance, which can inform decisions in real-world applications.

Related benchmarks:

Slice vs Splice vs Shift (Large Array 2) (version: 1)

Compares the speed for removing items from the beginning of an array

Comparing performance of: array.slice() vs array.splice() vs array.shift()

Created: 5 days ago by: Guest

Jump to the latest result

array.slice()

array.splice()

array.shift()

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 5 days ago):