Benchmark: Check variable vs check if key is in object

Script Preparation code:

var obj = {
  _items: [],
  _test: "abc",
  _var1: 100,
  _var2: 200,
  _type: 1
}

Tests:

Check variable
if(obj._type) { const x = 1; }
Check if object has a key
if('_type' in obj) { const x = 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Check variable
Check if object has a key

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark is designed to compare two approaches for checking the existence of a property in an object: using a variable assignment (`const x = 1;`) versus using the `in` operator (`'key' in obj`). The benchmark creates a sample object with various properties and then runs each test case repeatedly.

**Options Being Compared**

There are two main options being compared:

1. **Check Variable**: This option uses a variable assignment to check if a property exists. In this case, the code `const x = 1;` is assigned to evaluate if the `_type` property exists in the object.
2. **Check if Object has a Key**: This option uses the `in` operator to check if a key exists in an object. In this case, the code `'key' in obj` is used.

**Pros and Cons of Each Approach**

1. **Check Variable**:
	* Pros: Can be more readable and easier to understand for some developers, as it explicitly assigns a value.
	* Cons: May incur additional overhead due to variable assignment, which can lead to slower execution times.
2. **Check if Object has a Key**:
	* Pros: Generally faster, as it uses a built-in operator that doesn't require explicit assignments.
	* Cons: Can be less readable and more prone to errors, especially for developers who are not familiar with the `in` operator.

**Library Usage**

There is no specific library mentioned in the provided code. However, some browsers may have additional libraries or modules that can affect the execution times of this benchmark. For example, some browsers might use a caching mechanism for the `in` operator, which could impact performance.

**Special JS Features/Syntax**

The benchmark uses the following special feature:

* **Variable declarations**: The code uses `const x = 1;` to declare and initialize a variable. This is a feature introduced in ECMAScript 2015 (ES6) for declaring variables with block scope.
* **Template literals**: Although not used explicitly, template literals are mentioned in the script preparation code (`var obj = {\r\n ... }`). Template literals are a syntax feature introduced in ECMAScript 2015 (ES6) for creating string templates.

**Other Alternatives**

For similar benchmarks, consider using other approaches, such as:

* Using `hasOwnProperty()` on the object to check if a property exists.
* Utilizing `Object.keys()` or `Object.getOwnPropertyNames()` to iterate over an object's properties and check if a specific key exists.
* Employing a library like Lodash, which provides various utility functions for working with objects and arrays.

These alternatives may offer different trade-offs in terms of performance, readability, and maintainability.

Related benchmarks:

Check variable vs check if key is in object (version: 0)

Comparing performance of: Check variable vs Check if object has a key

Created: 3 years ago by: Registered User

Jump to the latest result

Check variable

Check if object has a key

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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