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

Script Preparation code:

var array = [1,2,3];

Tests:

array[array.length - 1]
var d = array[2];
array.at(-1)
var z = array.at(2);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array[array.length - 1]
array.at(-1)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 27 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
array[array.length - 1]	203063216.0 Ops/sec
array.at(-1)	203573744.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared, and their pros/cons.

**What is being tested:**

The test case compares two ways to access the last element of an array in JavaScript:

1. `array[array.length - 1]`: This method uses the square bracket notation (`[]`) to access the array element at the specified index.
2. `array.at(-1)`: This method uses the `at()` function (introduced in ECMAScript 2019) to access the array element at the specified index.

**Options compared:**

The two options are being compared in terms of their performance and execution speed.

**Pros/Cons of each approach:**

* `array[array.length - 1]`:
	+ Pros:
		- Wide browser support, as it's a standard JavaScript feature.
		- Easy to understand and implement for developers familiar with arrays.
	+ Cons:
		- May be slower than the optimized `at()` method due to the use of square brackets.
* `array.at(-1)`: (introduced in ECMAScript 2019)
	+ Pros:
		- Optimized for performance, as it's a native function designed specifically for array indexing.
		- Can be faster than the `array[array.length - 1]` method due to its optimized implementation.
	+ Cons:
		- Limited browser support, as not all browsers support this feature. In this benchmark, Chrome 122 is used, which supports it.

**Library/Functionality:**

In this case, no external library or function is being compared. The `at()` function is a built-in JavaScript method introduced in ECMAScript 2019.

**Special JS feature/syntax:**

The `at()` function is an example of a modern JavaScript feature that allows for more expressive and efficient array indexing. It's designed to provide a better alternative to the traditional `array[array.length - 1]` approach, especially when working with large arrays or arrays of objects.

**Other considerations:**

When choosing between these two approaches, consider the following factors:

* Browser support: If you need to support older browsers that don't have built-in `at()` function support, you may want to stick with `array[array.length - 1]`.
* Performance: If performance is critical and you're working with large arrays or arrays of objects, the optimized `at()` method might be a better choice.
* Code readability and maintainability: Both methods are readable and maintainable, but some developers might find `at()` more intuitive than using square brackets.

**Alternatives:**

If you need to support older browsers that don't have built-in `at()` function support or if you prefer not to use this modern JavaScript feature, other alternatives include:

* Using a library like Lodash's `get()` method
* Creating a custom array accessor function (e.g., `array.get(index)`)

However, these alternatives may come with additional complexity and potential performance overhead compared to the built-in `at()` function.

Related benchmarks:

array[index] vs array.at(index) (version: 0)

Comparing performance of: array[array.length - 1] vs array.at(-1)

Created: 9 months ago by: Guest

Jump to the latest result

array[array.length - 1]

array.at(-1)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):