Benchmark: .at vs [x] (with last)

Script Preparation code:

var k = new Array(10000).fill(Math.random()*1000).map(e=>(Math.random()*1000));

Tests:

x[0]
return k[0];
x.at(0)
return k.at(0);
x[0] (last item)
return k[k.length - 1];
x.at(-1)
return k.at(-1);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
x[0]
x.at(0)
x[0] (last item)
x.at(-1)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.5005.61 Safari/537.36

Browser/OS: Chrome 102 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
x[0]	16189466.0 Ops/sec
x.at(0)	8844868.0 Ops/sec
x[0] (last item)	8263472.0 Ops/sec
x.at(-1)	8906362.0 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 benchmark and explain what is being tested, the options compared, their pros and cons, and other considerations.

**Benchmark Purpose**

The benchmark measures the performance of three different ways to access the first element of an array in JavaScript:

1. Direct array indexing (`k[0]`)
2. Using the `at()` method with a positive index (`k.at(0)`)
3. Using the `at()` method with a negative index (`k.at(-1)`)

The benchmark also includes a test case that accesses the last element of the array by indexing into the array from the end using negative indices.

**Options Compared**

Here's a brief overview of each option:

1. **Direct Array Indexing**: Accessing the first element directly using `k[0]`.
	* Pros: Simple and straightforward.
	* Cons: May lead to slower performance if the array is large, as it requires calculating the index manually.
2. **`at()` Method with Positive Index**: Using the `at()` method with a positive index to access the first element (`k.at(0)`).
	* Pros: More efficient and safe than direct indexing, as it handles edge cases automatically.
	* Cons: Requires the use of the `at()` method, which may not be supported by older browsers or environments.
3. **`at()` Method with Negative Index**: Using the `at()` method with a negative index to access the last element (`k.at(-1)`).
	* Pros: Efficient and safe for accessing elements from the end of the array.
	* Cons: Requires a negative index, which may be less intuitive than using positive indices.

**Other Considerations**

The benchmark also includes test cases that cover different execution scenarios, such as:

* Accessing the first element directly (`k[0]`)
* Using the `at()` method with a positive index to access the first element (`k.at(0)`)
* Using the `at()` method with a negative index to access the last element (`k.at(-1)`)

The benchmark uses a large array of 10,000 elements filled with random values for each test case.

**Library and Syntax**

The `at()` method is a part of the modern JavaScript standard, introduced in ECMAScript 2019 (ES11). It provides a safe way to access elements from an array by index, without throwing an exception if the index is out of bounds.

No special JavaScript features or syntax are required for this benchmark. The tests only use standard JavaScript syntax and does not rely on any specific browser or environment quirks.

**Alternatives**

There are alternative ways to achieve similar performance in accessing elements from an array:

1. **Sliced Arrays**: Using slice() method to create a new array with the desired elements.
2. **Splice() Method**: Using splice() method to remove and return the first element of the array, or by adding an index argument for a negative index.

However, these alternatives may not provide the same level of performance as direct indexing or using the `at()` method.

Overall, this benchmark provides a good comparison of different ways to access elements from an array in JavaScript, highlighting the trade-offs between simplicity, safety, and performance.

Related benchmarks:

.at vs [x] (with last) (version: 0)

Comparing performance of: x[0] vs x.at(0) vs x[0] (last item) vs x.at(-1)

Created: 2 years ago by: Registered User

Jump to the latest result

x[0]

x.at(0)

x[0] (last item)

x.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):