Benchmark: Object key access vs array index access 100000

Script Preparation code:

var items = Array.from(
  Array(100000),
  (item, index) => ({ key: index, value: index*10 })
);
var objContainer = new Object();
var arrContainer = new Array(items.length);

// For a tenth of the number of items...
for (let i = items.length/10; i >= 0; i--) {
  // Choose a random item
  const index = Math.floor(Math.random() * items.length);
  const item = items[index];

  // Assign the item to the object and array containers
  objContainer[item.key] = item;
  arrContainer[item.key] = item;
}

Tests:

Object key access
items.forEach((item) => objContainer[item.key]?.value)
Array index access
items.forEach((item) => arrContainer[item.key]?.value)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object key access
Array index access

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object key access	185.5 Ops/sec
Array index access	321.7 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 JSON and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to compare the performance of accessing an item in two different ways:

1. **Object Key Access**: This involves accessing an item by its key in an object.
2. **Array Index Access**: This involves accessing an item by its index in an array.

In the benchmark preparation code, a large array `items` is created with 100,000 items, each having a unique key-value pair. The script then creates two containers: an object container (`objContainer`) and an array container (`arrContainer`). It randomly selects one item from the `items` array and assigns it to both the object and array containers.

**Options Compared**

The benchmark is comparing the performance of accessing an item by its key in an object versus accessing an item by its index in an array. The options being compared are:

* Object Key Access (using `objContainer[item.key]`)
* Array Index Access (using `arrContainer[item.key]`)

**Pros and Cons**

Here's a brief analysis of the pros and cons of each approach:

**Object Key Access:**

Pros:

* More intuitive and easier to read, especially for developers familiar with objects.
* Can be more efficient if the object is sparse (i.e., has many empty keys).

Cons:

* May be slower due to the need to resolve the key lookup using `objContainer[item.key]`.
* Requires additional memory allocation for the object container.

**Array Index Access:**

Pros:

* Typically faster, as it directly accesses the array element at the specified index.
* More memory-efficient, as only a single array is required.

Cons:

* Can be less intuitive and more prone to errors, especially for developers unfamiliar with arrays.
* May not work correctly if the array has many empty slots.

**Library Usage**

In this benchmark, no external libraries are explicitly mentioned. However, some JavaScript features like `Array.from()` (used in the script preparation code) and optional chaining (`?.`) (used in the benchmark definitions) might be considered libraries by some developers. These features are part of the standard JavaScript language and are widely supported across most browsers.

**Special JS Features/Syntax**

There is no specific special JavaScript feature or syntax used in this benchmark, other than what's inherent to the language itself.

**Other Alternatives**

If you were to rewrite this benchmark, you could consider exploring alternative approaches, such as:

* Using a data structure that combines both object and array features (e.g., a Map).
* Optimizing the script preparation code for better performance.
* Using more advanced profiling tools or benchmarking frameworks to gather more detailed results.

Keep in mind that these alternatives would require significant modifications to the benchmark code and might not yield significantly different results.

Related benchmarks:

Object key access vs array index access 100000 (version: 0)

Tests the speed of accessing an item by object key vs array index.

Comparing performance of: Object key access vs Array index access

Created: 8 months ago by: Guest

Jump to the latest result

Object key access

Array index access

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):