Benchmark: object property lookup: in operator vs undefined comparison

Script Preparation code:

var obj={prop:'dddd'};

Tests:

in operator
if ('prop' in obj);
!==undefined comparison
if (obj.prop!==undefined);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
in operator
!==undefined comparison

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Windows

View result in a separate tab

Test name	Executions per second
in operator	23867146.0 Ops/sec
!==undefined comparison	21404310.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and benchmark preparation code to understand what is being tested.

**Benchmark Definition**

The benchmark definition describes two different approaches to compare:

1. **"in operator"`**: This approach uses the `in` operator to check if a property (`prop`) exists in an object (`obj`). The `in` operator returns a boolean value indicating whether the property exists.
2. **"!==undefined comparison"`**: This approach compares the existence of a property (`prop`) in an object (`obj`) by checking if the property is not equal to `undefined`. This is done using the `!==` operator, which checks for both equality and identity.

**Pros and Cons**

1. **"in operator"`:
	* Pros: The `in` operator is a built-in operator in JavaScript and can be more readable when used with an array.
	* Cons: The `in` operator may introduce additional overhead due to the way it checks for property existence, especially if the object has many properties.
2. **"!==undefined comparison"`:
	* Pros: This approach avoids potential issues with the `in` operator and can be more efficient since it only checks for equality and identity.
	* Cons: The syntax may appear less readable compared to using the `in` operator.

**Library**

There is no explicit library mentioned in the provided JSON. However, the `obj` object is initialized with a property (`prop`) using JavaScript's variable declaration syntax.

**Special JS Features or Syntax**

The benchmark uses JavaScript's "string interpolation" feature introduced in ECMAScript 2015 (ES6). The string literals used in the script preparation code and individual test cases are enclosed in double quotes, which enables string interpolation. This feature allows for more readable and concise string formatting.

**Other Alternatives**

In addition to the two approaches tested, other alternatives could include:

* Using `hasOwnProperty()` method on objects to check if a property exists.
* Utilizing `for...in` loop with the `Object.keys()` method to iterate over an object's properties.
* Employing more advanced techniques like using `Map` or `Set` data structures to store and retrieve properties.

Keep in mind that these alternatives may introduce additional complexity, and their performance characteristics might differ from those of the tested approaches.

Related benchmarks:

object property lookup: in operator vs undefined comparison (version: 0)

Comparing performance of: in operator vs !==undefined comparison

Created: 4 years ago by: Registered User

Jump to the latest result

in operator

!==undefined comparison

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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