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: 7 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

Test name	Executions per second
includes	26375146.0 Ops/sec
lookup	1342648960.0 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.

Related benchmarks:

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

Comparing performance of: includes vs lookup

Created: 3 years ago by: Guest

Jump 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):