Benchmark: array includes vs object key lookup, large arrays

Script Preparation code:

var a = Array.from({length:500},(v,k)=>k+1)
var b = Object.assign({}, ...a.map((x) => ({[x]: true})));

Tests:

includes
return a.includes(9)
lookup
return b[9]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
includes
lookup

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Firefox/128.0

Browser/OS: Firefox 128 on Windows

View result in a separate tab

lookup

1342.6M/s

includes

26.4M/s

View exact numbers

Test name	Executions per second
✓ lookup	1,342,648,960 Ops/sec
includes	26,375,146 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand the provided benchmark.

**What is being tested?**

The benchmark is comparing two approaches:

1. `array.includes()` for checking if an element exists in an array (`"includes"` test case).
2. Direct key lookup on an object using square brackets (`"lookup"` test case).

**Options compared:**

The benchmark is comparing the performance of these two approaches when searching for a specific value (in this case, the number 9) in large arrays and objects.

**Pros and Cons of each approach:**

1. `array.includes()`: This method checks if the specified element exists in the array by iterating through it from start to end. It's relatively simple and straightforward.
	* Pros:
		+ Easy to implement and understand.
		+ Works well for most use cases.
	* Cons:
		+ Can be slower for large arrays, especially when searching for a specific element that is not near the beginning of the array.
2. Direct key lookup on an object using square brackets (`"lookup"` test case): This method directly accesses the property on the object using its key (in this case, `[9]`).
	* Pros:
		+ Can be faster for large objects when searching for a specific property that is close to the beginning of the object.
	* Cons:
		+ Requires knowledge of object keys and can lead to errors if not used correctly.

**Library usage:**

There is no explicit library mentioned in the provided benchmark. However, it's worth noting that `Array.from()` and `Object.assign()` are built-in JavaScript methods, which might be optimized under the hood by modern browsers.

**Special JS features or syntax:**

The benchmark uses the following special feature:

* `let` constants (e.g., `var a = Array.from({length:500},(v,k)=>k+1)`): This is a new way to declare variables in JavaScript, introduced in ECMAScript 2015. It allows for constant declarations that are scoped to the block or function.

**Other alternatives:**

If you were to reimplement this benchmark using different approaches, some alternative options could be:

* Using `for...of` loop with `find()` method on arrays.
* Using `Object.keys()` and indexing into an object property by its key index.
* Implementing a custom hash table or trie data structure for faster lookups.

However, without seeing the benchmark code, it's difficult to recommend alternative approaches that would yield similar results.

array includes vs object key lookup, large arrays (version: 0)

Comparing performance of: `includes vs lookup`

Created: 3 years ago by: Guest

Go to the latest result

includes

lookup

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

array includes vs object key lookup, large arrays (version: 0)

Comparing performance of: includes vs lookup

Created: 3 years ago by: Guest

Go to the latest result

includes

lookup

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `includes vs lookup`