Benchmark: instanceof vs constructor comparison

HTML Preparation code:

<script>
class TestClass {
    a = 0;
	b = 0;
    constructor() {
        this.a = 2;
    }
    get GetA() {
        return this.a;
    }
    GetB() {
        return this.b;
    }
}
</script>

Script Preparation code:

var obj = new TestClass();

Tests:

Instanceof
obj instanceof TestClass;
Constructor comparison
obj.constructor === TestClass;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Instanceof
Constructor comparison

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

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

**Benchmark Test Cases:**

The test consists of two individual test cases:

1. `obj instanceof TestClass;` (Instanceof)
2. `obj.constructor === TestClass;` (Constructor comparison)

**Options being compared:**

In both test cases, we're comparing the execution time or performance between two approaches:

*   **Instanceof**: Checking if an object is an instance of a particular constructor.
*   **Constructor comparison**: Directly comparing the constructor function of the object with the expected constructor.

**Pros and Cons of each approach:**

1.  **Instanceof**:
    *   Pros:
        *   More efficient, as it uses a single operation to check if an object is an instance of a particular class.
        *   Less dependent on the implementation details of the constructor.
    *   Cons:
        *   May not be directly comparable with `constructor comparison` due to differences in how they're implemented internally.
2.  **Constructor comparison**:
    *   Pros:
        *   More straightforward and easier to understand, as it's a direct comparison between two values (the object's constructor and the expected constructor).
    *   Cons:
        *   Generally slower than `instanceof` due to additional overhead from the comparison operation.

**Library used:**

There is no explicit library mentioned in the benchmark definition or script preparation code. However, the use of a custom class (`TestClass`) suggests that it's a JavaScript-specific implementation detail.

**Special JS feature/syntax:**

The benchmark uses JavaScript classes and their methods (`constructor`, `GetA`, and `GetB`). There are no special JavaScript features like async/await, arrow functions, or modern syntax elements mentioned in the code. The focus is on testing basic class-based object creation and comparison.

**Other alternatives:**

If you need to compare execution times for other scenarios, here are some potential alternatives:

*   Checking if an object has a certain property (e.g., `obj.hasOwnProperty('property')`) instead of using instanceof.
*   Using the `typeof` operator or the `instanceof` method on a prototype chain instead of directly comparing constructors.
*   Implementing custom equality checks between objects based on their attributes.

Keep in mind that these alternatives might introduce additional overhead, complexity, or implementation-specific differences, which could affect benchmark results.

Related benchmarks:

instanceof vs constructor comparison (version: 0)

Comparing performance of: Instanceof vs Constructor comparison

Created: 2 years ago by: Guest

Jump to the latest result

Instanceof

Constructor comparison

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):