Benchmark: `Array.slice(-1)[0]` vs `Array[Array.length]` for 10000 length

Script Preparation code:

var arr = Array.from(Array(10000).keys());

Tests:

`Array.slice(-1)[0]`
arr.slice(-1)[0];
`Array[Array.length]`
arr[arr.length-1];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
`Array.slice(-1)[0]`
`Array[Array.length]`

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.129 Safari/537.36

Browser/OS: Chrome 81 on Mac OS X 10.15.3

View result in a separate tab

Test name	Executions per second
`Array.slice(-1)[0]`	10088678.0 Ops/sec
`Array[Array.length]`	7853367.0 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 definition and test cases.

**What is tested?**

The main goal of this benchmark is to compare two approaches for accessing the last element of an array in JavaScript:

1. `Array.slice(-1)[0]`
2. `arr[arr.length-1]`

In other words, both methods aim to retrieve the last element of a large array (`arr` with 10,000 elements). The benchmark measures which method performs better.

**Options compared**

We have two options being compared:

a. **Dynamic property access**: `arr[arr.length-1]`
b. **Method chaining with slice()**: `Array.slice(-1)[0]`

Both methods are used to access the last element of an array, but they differ in how they achieve it.

**Pros and Cons**

**Dynamic Property Access (`arr[arr.length-1]`)**

Pros:

* More concise and expressive syntax.
* Can be more readable for those familiar with this pattern.

Cons:

* May incur additional overhead due to dynamic property access.
* Could lead to performance issues if not implemented correctly (e.g., using a large number of intermediate variables).

**Method Chaining with Slice() (`Array.slice(-1)[0]`)**

Pros:

* Often more efficient, as slice() is a native method that can be optimized by the JavaScript engine.
* Can provide better cache locality and reduce memory allocations.

Cons:

* May require more code to express the same intent (e.g., `arr.length-1`, `Array.slice(-1)`).
* Less readable for those unfamiliar with this pattern.

**Library usage**

There is no library explicitly mentioned in the benchmark definition. However, it's worth noting that some libraries like Lodash might provide similar functionality or alternatives to these approaches.

**Special JS feature/syntax**

None are explicitly mentioned. The syntax used here is standard JavaScript.

**Other considerations**

* **Array creation**: The array `arr` is created using `Array.from(Array(10000).keys())`, which generates an array of 10,000 numbers from 0 to 9,999.
* **Benchmarking**: The benchmark measures the executions per second for each test case. This provides insight into the performance differences between the two approaches.

**Other alternatives**

If you're interested in exploring other approaches or optimizing these methods further, consider looking into:

* Using `Array.prototype.at()` (supported in modern browsers and Node.js), which is a more concise and expressive way to access array elements.
* Implementing your own optimized version of the last element access method using assembly language or native code.

Keep in mind that optimizations should be carefully evaluated for their impact on readability, maintainability, and overall performance.

Related benchmarks:

`Array.slice(-1)[0]` vs `Array[Array.length]` for 10000 length (version: 0)

Comparing performance of: `Array.slice(-1)[0]` vs `Array[Array.length]`

Created: 4 years ago by: Guest

Jump to the latest result

`Array.slice(-1)[0]`

`Array[Array.length]`

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):