Benchmark: Instanceof vs constructor.name

HTML Preparation code:

<script>
class TestClass {
    constructor() {
        this.a = 2;
        this.t = 'mesh';
    }
}
</script>

Script Preparation code:

var obj = new TestClass();

Tests:

instanceof
obj instanceof TestClass;
property
obj.constructor.name === "TestClass"
constructor comparison
obj.constructor === TestClass

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
property
constructor comparison

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):

LLMs can make mistakes. Check important info.

### Benchmark Overview

This benchmark tests the performance of different methods for checking the type of a JavaScript object. It compares three approaches:

1. **Using `instanceof`**: Checks if an object is an instance of a specific class.
   - **Code**: `obj instanceof TestClass;`
   - **Test Name**: "instanceof"

2. **Comparing `constructor.name` to a string**: Checks if the name of the constructor matches a specific string.
   - **Code**: `obj.constructor.name === "TestClass";`
   - **Test Name**: "property"

3. **Directly comparing the `constructor` property to the class**: Compares the `constructor` property directly to the specific class constructor.
   - **Code**: `obj.constructor === TestClass;`
   - **Test Name**: "constructor comparison"

### Comparative Analysis

#### 1. Using `instanceof`
- **Pros**: 
  - Robust against inheritance: `instanceof` will also return `true` for objects that were created from subclasses of `TestClass`, which can be beneficial if your application relies heavily on inheritance.
  - Readable: It clearly indicates the relational type of the object.
- **Cons**: 
  - Slightly slower performance compared to property-based checks, as it involves checking the prototype chain.
  
#### 2. Comparing `constructor.name`
- **Pros**:
  - Can be easily used in scenarios where you do not need strict type checking with inheritance. It relies on string matching, which can be straightforward.
  - Readability is high as it's clear you're checking the name directly.
- **Cons**:
  - Prone to issues with minification: If the code is minified, the constructor name could be changed, leading to false negatives.
  - It may not work as expected in scenarios where the object might have had its constructor changed or is created with a different constructor.

#### 3. Direct Constructor Comparison
- **Pros**:
  - Fast performance because it is a direct property look-up with no string comparison or prototype chain traversal.
  - Reliable in environments where constructors are not changed or altered.
- **Cons**:
  - Less flexible: This approach doesn't account for inheritance hierarchies, meaning it will only return true for instances of `TestClass` directly, not for its derived classes.

### Results Summary
From the benchmark results, we observe the following executions per second for each approach:
- **Best Method**: Comparing `constructor.name` yielded the highest performance at approximately **25,596,230** executions/second.
- **Next Best Method**: Direct constructor comparison followed, achieving about **13,887,711** executions/second.
- **Least Efficient**: The `instanceof` method was the slowest, with **13,252,405** executions/second.

### Other Considerations
- **Browser Compatibility**: The tests were conducted on Chrome version 130 for a Linux desktop, and results may vary across different browsers or versions. Testing across multiple environments is crucial for performance-driven applications.
- **Use Cases**: The choice between these methods often depends on the application requirements. Code that relies on inheritance should likely opt for `instanceof`, while performance-critical applications may want to weigh the speed of constructor comparisons.
- **Alternatives**: Other alternatives include the use of `Object.prototype.toString.call(obj)` for checking types or using a utility library like Lodash which provides methods like `_.isObject` and `_.isArray` that perform type checks but may not be directly comparable in performance without specific use cases.

Overall, developers should choose the approach that balances performance, readability, and the specific needs of their applications, keeping in mind the potential pitfalls of each method.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Linux

View result in a separate tab

Test name	Executions per second
instanceof	13252405.0 Ops/sec
property	25596230.0 Ops/sec
constructor comparison	13887711.0 Ops/sec

Related benchmarks:

Instanceof vs constructor.name (version: 0)

Measure the performance of instanceOf operator vs comparing a basic string type.

Comparing performance of: instanceof vs property vs constructor comparison

Created: one month ago by: Registered User

Jump to the latest result

instanceof

property

constructor comparison

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):