Benchmark: instanceof vs in

Script Preparation code:

var obj = {a:2};

Tests:

instanceof
obj instanceof Object
in
'a' in obj
not nil
!!obj.a

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
in
not nil

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 26 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:132.0) Gecko/20100101 Firefox/132.0

Browser/OS: Firefox 132 on Windows

View result in a separate tab

Test name	Executions per second
instanceof	242590720.0 Ops/sec
in	1493049344.0 Ops/sec
not nil	1470953856.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what's being tested.

**Benchmark Definition**

The benchmark is defined by a single JSON object with four properties:

* `Name`: A descriptive name for the benchmark, which in this case is "instanceof vs in ".
* `Description`: An empty string indicating that no description is available.
* `Script Preparation Code`: A JavaScript code snippet that initializes an object `obj` with a property `a` set to 2. This object will be used as input for the benchmarks.
* `Html Preparation Code`: An empty string, indicating that no HTML setup is required.

**Individual Test Cases**

The benchmark consists of three test cases, each defined by another JSON object:

1. **`instanceof`**: Verifies if the `obj instanceof Object` condition returns true.
	* Purpose: Tests the use of the `instanceof` operator to check if an object is a subclass of `Object`.
2. **`in`**: Verifies if the `'a' in obj` condition returns true.
	* Purpose: Tests the use of the `in` operator to check if a property exists in an object.
3. **`not nil`**: Verifies if `!!obj.a` returns true (i.e., the value of `obj.a` is not null or undefined).
	* Purpose: Tests a simple boolean condition using double negation.

**Pros and Cons of Different Approaches**

1. **`instanceof`**: This approach checks if the object is an instance of the specified class, which can be useful for subclass checking. However, it may have performance overhead due to the use of reflection.
2. **`in`**: The `in` operator is generally faster and more efficient than `instanceof`, as it only checks the property's existence in the object. It also provides better support for arrays and other collections.
3. **`not nil`**: This approach uses double negation, which can be confusing and may lead to performance issues if not used carefully.

**Library Usage**

None of the test cases use a library explicitly, but they do utilize built-in JavaScript operators (`instanceof`, `in`) and functions (`!!`). The `!!` operator is a part of the ECMAScript standard, so it's generally considered safe to use in most environments.

**Special JS Features or Syntax**

The benchmark uses the following special features:

1. **Double Negation (`!!`)**: This syntax is used to negate a boolean value. It's generally allowed in modern JavaScript engines but may not work as expected in older versions.
2. **Property Access (`obj.a`)**: This syntax assumes that `a` is a property of the `obj` object.

**Other Alternatives**

If you want to write similar benchmarks, consider using alternative approaches:

1. Use existing testing libraries like Jest or Mocha, which provide more advanced features and flexibility.
2. Utilize other comparison operators, such as `===`, `!==`, or `typeof`.
3. Experiment with different property access patterns, such as bracket notation (`obj['a']`) or dot notation (`obj.a`).

Related benchmarks:

instanceof vs in (version: 0)

Comparing performance of: instanceof vs in vs not nil

Created: 2 years ago by: Guest

Jump to the latest result

instanceof

in

not nil

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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