Benchmark: set.has vs. Object key in lookup

Script Preparation code:

var a = new Set([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
var b = {1: true, 2: true, 3: true, 4: true, 5: true, 6: true, 7: true, 8: true, 9: true, 10: true}

Tests:

set.has
return a.has(9)
key in
return 9 in b;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
set.has
key in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.3.1 Safari/605.1.15

Browser/OS: Safari 17 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
set.has	460671392.0 Ops/sec
key in	366664608.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the benchmark and explain what's being tested.

**What is being tested?**

The benchmark compares two approaches to check if a value exists in an object or a Set data structure:

1. `set.has()`: This method is part of the built-in `Set` object in JavaScript, which allows you to check if a specific value exists within the set.
2. `"9 in b"`: This syntax uses the "in" operator to check if a value (in this case, `9`) is present as a key in an object (`b`).

**Options compared**

The two options being compared are:

* `set.has()`: This method is fast and efficient because it uses a hash table to store the set's elements. Looking up a value in a set involves a constant-time operation (O(1)).
* `"9 in b"`: This syntax involves iterating over the object's keys using the "in" operator, which has an average time complexity of O(1) for modern browsers, but can be slower than `set.has()` due to additional overhead.

**Pros and Cons**

* `set.has()`:
	+ Pros:
		- Fast and efficient (O(1))
		- Built-in method with minimal overhead
	+ Cons:
		- Only supported in modern browsers that support the Set object
		- May not work as expected in older browsers or environments without a Set object
* `"9 in b"`:
	+ Pros:
		- Works in most browsers and environments
		- Doesn't rely on any specific libraries or APIs
	+ Cons:
		- Slower than `set.has()` (O(1) average, but can be slower due to additional overhead)
		- More verbose syntax

**Library**

In the provided benchmark code, there is no explicit library being used. However, it's worth noting that if you were to use a library like Lodash or Underscore.js, which provide utility functions for working with objects and sets, they might offer implementations of `set.has()`-like functionality.

**Special JS feature**

There are no special JavaScript features or syntax being tested in this benchmark. It's a straightforward comparison between two common approaches to checking if a value exists in an object or set.

**Other alternatives**

If you're looking for alternative ways to check if a value exists in an object, some other options include:

* Using the `Object.prototype.hasOwnProperty.call()` method: This is another way to check if a property exists on an object.
* Using a library like Lodash's `_.has()` function: This function provides a flexible and efficient way to check if a value exists in an object or array.

Keep in mind that the best approach often depends on your specific use case, performance requirements, and target browser support.

Related benchmarks:

set.has vs. Object key in lookup (version: 0)

Comparing performance of: set.has vs key in

Created: one year ago by: Guest

Jump to the latest result

set.has

key in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):