Benchmark: how to get last array element

HTML Preparation code:

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Script Preparation code:

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async function globalMeasureThatScriptPrepareFunction() {
    // This function is optional, feel free to remove it.
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Tests:

slice and index
var array = [0,1,2,3,4,5,6,7,8,9,10]; var result = array.slice(-1)[0];
spread and pop
var array = [0,1,2,3,4,5,6,7,8,9,10]; var result = [...array].pop();
get by length
var array = [0,1,2,3,4,5,6,7,8,9,10]; var result = array[array.length - 1];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice and index
spread and pop
get by length

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 14 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Whale/4.30.291.11 Safari/537.36

Browser/OS: Chrome 132 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
slice and index	68380208.0 Ops/sec
spread and pop	68780424.0 Ops/sec
get by length	251725984.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 14 days ago):

LLMs can make mistakes. Check important info.

The provided benchmark evaluates different methods to retrieve the last element of a JavaScript array. Three distinct test cases are implemented, each using a different approach, allowing for a direct comparison of their performance. Here is a breakdown of each method, its pros and cons, and alternative strategies.

### Test Cases:

1. **Slice and Index**
   - **Code:** `var result = array.slice(-1)[0];`
   - **Method Explained:** This approach utilizes the `slice` method to create a new array containing the last element of the original array and then accesses that element using indexing.
   - **Pros:**
     - Clear and straightforward syntax, beneficial for readability.
     - Works with negative indices which can be useful in more complex scenarios.
   - **Cons:**
     - Creates a new array, thereby incurring additional memory overhead.
     - Potentially slower due to the extra step of creating a new array.

2. **Spread and Pop**
   - **Code:** `var result = [...array].pop();`
   - **Method Explained:** This approach uses the spread operator (`...`) to create a shallow copy of the original array and then employs the `pop` method to remove and return the last element of the copied array.
   - **Pros:**
     - The spread operator can be quite versatile, making this method applicable in various situations where array copying is needed.
   - **Cons:**
     - Similar to the first method, it creates a new array in memory, leading to increased memory usage and performance costs.
     - The `pop` method modifies the array, which, combined with spreading, can lead to confusion about the original array's integrity.

3. **Get by Length**
   - **Code:** `var result = array[array.length - 1];`
   - **Method Explained:** This straightforward approach retrieves the last element directly by calculating the index using the array's `length` property.
   - **Pros:**
     - Most efficient in terms of both speed and memory usage, as it does not create any additional arrays.
     - Very clear and easy to understand for anyone familiar with JavaScript.
   - **Cons:**
     - Lacks the flexibility that methods utilizing slicing or spreading offer.

### Benchmark Results Analysis
From the benchmark results, we see the following performance outcomes:

- **Get by Length** approach had the highest executions per second at **251,725,984**, indicating that it is the most efficient method for this operation.
- **Spread and Pop** performed moderately with **68,780,424** executions per second, and was followed closely by **Slice and Index** with **68,380,208** executions per second. Both of these approaches are dramatically slower due to their memory allocation overhead.

### Other Considerations and Alternatives
- **Memory Usage:** The `slice` and `spread` methods' creation of new arrays can lead to performance degradation, especially with larger arrays. In scenarios where performance is critical—such as in real-time data processing or when processing large arrays—avoiding unnecessary memory allocation is essential.
- **Alternatives:** 
  - `array.at(-1)` is another option available in modern JavaScript, which allows for retrieving the last element directly with negative indexing without creating a new array. This might provide a balance of readability and performance.
  - For performance-sensitive applications, consider using typed arrays (e.g., `Uint8Array`, `Float32Array`) which provide better performance for numerical computations.

In conclusion, while there are various methods to retrieve the last element of an array in JavaScript, the simplest and most efficient technique is to use the array's length as an index. This comparison highlights the trade-offs between code readability and performance, which is a common consideration in software engineering.

Related benchmarks:

how to get last array element (version: 1)

Comparing performance of: slice and index vs spread and pop vs get by length

Created: 14 days ago by: Guest

Jump to the latest result

slice and index

spread and pop

get by length

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 14 days ago):