Benchmark: key exists: key in object vs !!object[key] vs object[key]

Script Preparation code:

testObject = {'asdf': 'apple', 'afwefg': 'pear', 'hohoo': 'santa', 'country': 'usa', 'bottle': 'gin'};

Tests:

key in object
'afwefg' in testObject
!!object[key]
!!testObject['afwefg']
object[key]
testObject['afwefg']

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
key in object
!!object[key]
object[key]

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested.

**Benchmark Definition**

The benchmark measures the performance difference between three approaches:

1. `key in object`: This checks if a key exists in an object using the `in` operator.
2. `!!object[key]`: This uses the logical not operator (`!!`) to check if the value of the specified key is falsy. Since `Object.keys()` returns an array of keys, and empty arrays are considered falsy, this approach essentially checks if the key exists in the object.

The purpose of this benchmark is to compare the performance of these two approaches: checking for existence using the `in` operator versus using a conditional expression with logical not.

**Pros and Cons**

* **`key in object`**:
	+ Pros: Simple, readable, and easy to understand. This approach has been the standard way to check if a key exists in an object since JavaScript 1.0.
	+ Cons: May be slower due to the overhead of checking for existence using `in`.
* `!!object[key]`:
	+ Pros: Can be faster than the traditional `key in object` approach, especially when dealing with large objects or arrays.
	+ Cons: May be less readable and more confusing for developers who are not familiar with this syntax.

**Library and Special JS Features**

In this benchmark, no libraries are explicitly mentioned. However, it's essential to note that using the `in` operator checks if the property exists in the object's prototype chain. If you want to check only the own properties of an object (i.e., not its prototype), you would need to use `Object.hasOwnProperty()`.

**Other Considerations**

When writing microbenchmarks like this one, it's essential to consider factors beyond performance:

* **Code readability**: How easy is the code to understand and maintain?
* **Real-world applicability**: Are these approaches applicable to real-world scenarios or edge cases?
* **Browser support**: What browsers do you want to test for?

**Alternatives**

If you need to benchmark similar expressions, consider testing other approaches, such as:

* `Object.prototype.hasOwnProperty.call()` (if you're targeting older browsers)
* Using `Array.isArray()` and `typeof` to check if a value is an array or object
* Utilizing modern features like `hasOwnProperty()` on objects

Keep in mind that each approach has its own trade-offs, and the best solution depends on your specific use case.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Linux; Android 8.0.0; SM-G950U1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.80 Mobile Safari/537.36

Browser/OS: Chrome Mobile 70 on Android 8.0.0

View result in a separate tab

Test name	Executions per second
key in object	1965422.4 Ops/sec
!!object[key]	2447303.5 Ops/sec
object[key]	2450138.0 Ops/sec

Related benchmarks:

key exists: key in object vs !!object[key] vs object[key] (version: 0)

Comparing performance of: key in object vs !!object[key] vs object[key]

Created: 6 years ago by: Guest

Jump to the latest result

key in object

!!object[key]

object[key]

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):