Benchmark: InstanceOf vs flag

HTML Preparation code:

<script>
class TestClass {
    constructor() {
        this.a = 2;
        this.t = 1;
    }
}
</script>

Script Preparation code:

var obj = new TestClass();

Tests:

instanceof
obj instanceof TestClass;
flag check
obj.t === 1

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
flag check

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36

Browser/OS: Chrome 124 on Windows

View result in a separate tab

Test name	Executions per second
instanceof	9125491.0 Ops/sec
flag check	21100930.0 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 benchmark and its test cases.

**Benchmark Definition Json**

The provided JSON defines two microbenchmarks:

1. `InstanceOf vs flag`: This benchmark measures the difference in performance between using the `instanceof` operator versus simply checking if a property equals 1 (a "flag check").
2. `flag check`: This is another benchmark that only checks if a property (`obj.t`) equals 1.

**Script Preparation Code**

The script preparation code defines a class `TestClass` with two properties: `a` and `t`. The constructor initializes these properties with values 2 and 1, respectively.

**Html Preparation Code**

The HTML preparation code generates an HTML page that includes the JavaScript code for defining the `TestClass` class.

**Individual Test Cases**

There are two test cases:

1. **InstanceOf**: This test case measures the performance of using the `instanceof` operator to check if an object is an instance of `TestClass`. The benchmark definition uses `obj instanceof TestClass;`.
2. **flag check**: This test case measures the performance of simply checking if a property (`obj.t`) equals 1, without using the `instanceof` operator.

**Pros and Cons**

Here are some pros and cons for each approach:

* **InstanceOf**: Using `instanceof` provides type safety and can be more readable in some cases. However, it may incur additional overhead due to the need for dynamic typing at runtime.
* **flag check**: This approach is simpler and may be faster, but it loses type safety benefits and may be less readable.

**Other Considerations**

* The use of `instanceof` versus a flag check can have implications for code maintainability, readability, and performance. Developers should consider the trade-offs when choosing one approach over the other.
* The benchmark results show that Chrome 124 performs better for the `flag check`, while the `InstanceOf` test case is closer in performance.

**Library**

There is no explicit library mentioned in the provided JSON. However, it's likely that some libraries or built-in JavaScript features are being used under the hood to implement these tests (e.g., the `instanceof` operator).

**Special JS Features/Syntax**

The benchmark uses the following special JavaScript feature:

* **Dynamic typing**: The use of `obj instanceof TestClass;` and `obj.t === 1` relies on dynamic typing, which can affect performance.

**Alternatives**

There are other alternatives for implementing these tests, such as:

* Using a static type checker like TypeScript to enforce type safety at compile-time.
* Implementing a custom comparison function for the `flag check` test case.
* Using a different JavaScript engine or interpreter that optimizes one of these approaches over the others.

Overall, this benchmark provides a useful comparison between two common approaches in JavaScript development: using `instanceof` versus a flag check. By understanding the pros and cons of each approach, developers can make informed decisions about their own coding practices.

Related benchmarks:

InstanceOf vs flag (version: 0)

Comparing performance of: instanceof vs flag check

Created: 2 years ago by: Guest

Jump to the latest result

instanceof

flag check

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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