Benchmark: array[array.length] vs array.at(array.length)

Script Preparation code:

var array = [1,2,3];

Tests:

array[array.length]
var d = array[array.length];
array.at(array.length)
var z = array.at(array.length);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array[array.length]
array.at(array.length)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one month ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
array[array.length]	10444603.0 Ops/sec
array.at(array.length)	10095581.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):

LLMs can make mistakes. Check important info.

The benchmark you provided compares two different methods of accessing an element from an array in JavaScript: using the square bracket notation (`array[array.length]`) and using the `Array.prototype.at()` method (`array.at(array.length)`).

### Options Compared

1. **Square Bracket Notation**: `array[array.length]`
   - **Description**: This method accesses an element at a specified index within the array using brackets. The index is calculated as the length of the array, which generally leads to an out-of-bounds access since it typically corresponds to a position one unit beyond the last element of the array.
   - **Pros**: This is the traditional way of accessing array elements in JavaScript and is widely recognized and used. It’s straightforward and is generally fast for most use cases as it's how JavaScript arrays were originally designed.
   - **Cons**: Accessing `array[array.length]` in this context will always retrieve `undefined` when the array is empty, or it will access an out-of-bounds element when the array has elements, leading to potential confusion. It's not as intuitive when trying to retrieve the last element, as you would rather want `array[array.length - 1]` for that purpose.

2. **Array.prototype.at() Method**: `array.at(array.length)`
   - **Description**: The `at()` method is a relatively new addition to JavaScript (introduced in ES2022) and allows you to access elements from an array using a zero-based index. It is particularly beneficial as it also allows negative integers, which count back from the last element.
   - **Pros**: One of the key advantages is its ability to handle negative integers, allowing access to elements straightforwardly from the end of the array (e.g., `array.at(-1)` fetches the last element directly). It improves code readability and simplifies certain tasks like obtaining the last element.
   - **Cons**: Older browsers and environments that do not support ES2022 may not support this method, potentially leading to compatibility issues. Developers should ensure that they include proper polyfills if compatibility with older environments is necessary.

### Benchmark Results

The benchmark results show that the square bracket notation achieved approximately 10,444,603 executions per second, while the `at()` method achieved around 10,095,581 executions per second in the same environment. From these results:
- The array indexing performance is slightly faster than the `at()` method in this particular test.
- However, performance may vary depending on the context, the size of the arrays being used, and the JavaScript engine implementation.

### Other Considerations

1. **Readability and Maintainability**: For teams or projects focusing on code readability, the `at()` method can be preferable, especially when working with last elements, due to its clear and direct syntax.
2. **Accessibility for New Developers**: New developers often find the array bracket notation intuitive, though `at()` may be easier to grasp semantically for getting the last item in a list.
3. **Browser and Environment Compatibility**: Ensuring that the chosen method is compatible with the target audience's environments is critical, especially if certain browsers do not fully implement the new `Array.prototype.at()` method.

### Alternatives

Apart from the discussed methods, some alternatives exist for accessing the last element in an array:
- **`array.slice(-1)[0]`**: This approach returns a new array containing the last element, which might be less performant due to the creation of a temporary array.
- **Direct Index Access**: Using `array[array.length - 1]`, which provides more clarity when you specifically want the last element and avoids out-of-bounds issues.

Ultimately, the choice between these methods may depend on the specific context in which they're used, the target environment, and team preferences regarding code style and maintainability.

Related benchmarks:

array[array.length] vs array.at(array.length) (version: 1)

Comparing performance of: array[array.length] vs array.at(array.length)

Created: one month ago by: Guest

Jump to the latest result

array[array.length]

array.at(array.length)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):