Benchmark: array[array.length - 1] vs array.at(-1)

Script Preparation code:

var array = [1,2,3];

Tests:

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

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: 3 days ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Linux

View result in a separate tab

Test name	Executions per second
array[array.length - 1]	88945480.0 Ops/sec
array.at(-1)	90391968.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the benchmark.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark test case for two different ways of accessing the last element of an array: using `array[array.length - 1]` and `array.at(-1)`. The benchmark aims to compare the performance of these two approaches.

**Options Compared**

The benchmark compares two options:

1. **`array[array.length - 1]`**: This approach uses the standard array indexing syntax, where you access an element at a specific index using square brackets (`[]`). In this case, it's accessing the last element by subtracting 1 from the array length.
2. **`array.at(-1)`**: This approach uses the `at()` method, introduced in ECMAScript 2019 (ES11), which allows you to access elements at a specific index without having to worry about out-of-bounds errors.

**Pros and Cons**

Here are some pros and cons of each approach:

* **`array[array.length - 1]`**:
	+ Pros:
		- Widely supported in older browsers.
		- No additional library or feature required.
	+ Cons:
		- May require more careful handling to avoid out-of-bounds errors.
		- Less readable and maintainable, especially for larger arrays.
* **`array.at(-1)`**:
	+ Pros:
		- More concise and expressive syntax.
		- Better support for array bounds checking, reducing the risk of errors.
	+ Cons:
		- Requires ECMAScript 2019 (ES11) or later, which may not be supported in older browsers.

**Library**

In this benchmark, the `at()` method is used from the ECMAScript Standard Library. The purpose of `at()` is to provide a more expressive and safe way of accessing array elements at a specific index.

**Special JavaScript Feature**

The benchmark uses the `at()` method, which was introduced in ECMAScript 2019 (ES11). This feature allows you to access elements at a specific index using a safer and more readable syntax than traditional indexing.

**Other Considerations**

When considering these approaches, keep in mind that:

* For small arrays, the difference in performance may be negligible.
* For larger arrays or performance-critical code, `array.at(-1)` might offer a slight performance advantage due to its bounds checking.
* The choice between these approaches ultimately depends on your specific use case and the trade-offs you're willing to make between readability, maintainability, and performance.

**Other Alternatives**

If you need alternative ways to access array elements, consider:

* `array[-1]` (negative indexing): Accessing an element at a negative index, which can be useful for certain use cases.
* `array[Array.prototype.length - 1]`: Another way to access the last element of an array using standard indexing syntax.

Keep in mind that these alternatives may have different performance characteristics or trade-offs compared to the `at()` method.

Related benchmarks:

array[array.length - 1] vs array.at(-1) (version: 0)

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

Created: 2 years ago by: Registered User

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):