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

Script Preparation code:

  const LENGTH = 10000;

  var arr = new Array(LENGTH);

  for (let i = 0; i < LENGTH; i++) {
    arr[i] = i * 5;
  }

Tests:

at
arr.at(753);
bracket notation
arr[753];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
at
bracket notation

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/140.0.0.0 Safari/537.36

Browser/OS: Chrome 140 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
at	280331872.0 Ops/sec
bracket notation	257133712.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the provided JavaScript microbenchmark, MeasureThat.net.

**Benchmark Definition and Purpose**

The benchmark measures the performance of accessing elements in an array using two different approaches: `arr.at(index)` and `arr[index]`. The purpose is to compare the efficiency of these two methods.

**Options Compared**

There are two options being compared:

1. `arr.at(index)`
2. `arr[index]`

**Pros and Cons of Each Approach**

* `arr.at(index)`: This method uses the `at()` function, which was introduced in ECMAScript 2019. It provides a safer way to access array elements by throwing a `TypeError` if the index is out of bounds.
	+ Pros: Provides better error handling, more explicit syntax.
	+ Cons: May incur additional overhead due to the `TypeError` check.
* `arr[index]`: This method uses direct array indexing using square brackets (`[]`).
	+ Pros: Fast and simple, well-established syntax.
	+ Cons: No error checking, may lead to runtime errors if index is out of bounds.

**Other Considerations**

When accessing array elements, other factors that might affect performance include:

* Array length and density (i.e., how densely populated the array is).
* The browser's optimization techniques for array access.
* The availability of advanced features like WebAssembly or Just-In-Time (JIT) compilation.

**Library and Special JS Feature**

There is no library used in this benchmark. However, the `at()` function, which is being compared to direct indexing, is a special JavaScript feature introduced in ECMAScript 2019.

**Benchmark Preparation Code**

The preparation code creates an array of length 10,000 and populates it with values from 0 to 49,999 (i.e., each element is multiplied by 5).

**Individual Test Cases**

There are two test cases:

1. `arr.at(753)`: This tests the performance of accessing a specific element at index 753 using the `at()` function.
2. `arr[753]`: This tests the performance of accessing the same element at index 753 using direct array indexing.

**Benchmark Results**

The latest benchmark results show that:

* `arr.at(753)` has an execution rate of approximately 285,501,780 per second on a Desktop with Opera 102 browser.
* `arr[753]` has an execution rate of approximately 284,513,760 per second on the same setup.

In general, direct array indexing (`arr[index]`) tends to be faster than using the `at()` function due to the additional overhead introduced by error checking. However, the performance difference may vary depending on specific use cases and browser implementations.

Related benchmarks:

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

Comparing performance of: at vs bracket notation

Created: 2 years ago by: Guest

Jump to the latest result

at

bracket notation

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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