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

Script Preparation code:

var array = [1,2,3];

Tests:

array[array.length - 1]
var d = array[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: 6 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36

Browser/OS: Chrome 141 on Windows

View result in a separate tab

Test name	Executions per second
array[array.length - 1]	136308560.0 Ops/sec
array.at(-1)	131069320.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark being tested.

**What is being tested?**

The provided JSON represents a JavaScript microbenchmark that compares two approaches to access the last element of an array:

1. `array[array.length - 1]`
2. `array.at(-1)`

These two expressions are being compared to measure their performance difference.

**Options compared:**

* `array[array.length - 1]`: This approach uses a property access method to access the last element of the array. It requires calculating the length of the array and then using that value as an index.
* `array.at(-1)`: This approach uses the `at()` method, which is a relatively new feature introduced in ECMAScript 2020 (ES2020). The `at()` method allows indexing into arrays with a negative offset, making it more readable and concise than the traditional array indexing syntax.

**Pros and cons of each approach:**

* `array[array.length - 1]`:
	+ Pros: widely supported in older browsers, easier to understand for those familiar with traditional array indexing.
	+ Cons: can be slower due to the additional calculation required to determine the index.
* `array.at(-1)`: 
	+ Pros: more readable and concise, faster execution, better support in newer browsers.
	+ Cons: requires a modern browser that supports ES2020, may be less familiar for those without experience with this syntax.

**Library usage:**

The benchmark does not explicitly use any external libraries. However, it relies on the `at()` method, which is a built-in feature of JavaScript arrays in newer browsers (specifically, Chrome 115 and Safari 537.36).

**Special JS features or syntax:**

The benchmark uses the new `at()` method, which was introduced in ES2020. This syntax allows for more readable and concise indexing into arrays.

**Other alternatives:**

If you needed to support older browsers or want a different approach, here are some alternative methods:

* Using `slice()` method to extract the last element: `array.slice(-1)[0]`
* Using the `[Symbol.iterator]` method to iterate over the array and access the last element: `for (let i of array) { if (i === 2) { console.log(i); } }`

Keep in mind that these alternatives may have different performance characteristics compared to the original approaches being tested.

**Why this benchmark is interesting:**

This benchmark highlights the importance of considering performance and code readability when writing JavaScript. The use of `at()` method demonstrates a new feature that can improve code quality, while still being compatible with older browsers.

Related benchmarks:

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

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

Created: 2 years ago by: Guest

Jump to the latest result

array[array.length - 1]

array.at(-1)

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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