Benchmark: instanceof vs undefined prop

Script Preparation code:

var obj = {a:2};

Tests:

instanceof
obj instanceof Object
checking prop
obj.a === true

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
instanceof
checking prop

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 11 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Windows

View result in a separate tab

Test name	Executions per second
instanceof	92448728.0 Ops/sec
checking prop	91692416.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand the provided benchmark!

**What is being tested?**

The test cases measure the performance of two different approaches:

1. **`obj instanceof Object`**: This checks if an object `obj` has a prototype that is an instance of the `Object` class.
2. **`obj.a === true`**: This checks if the value of property `a` in the object `obj` is equal to `true`.

**What are the pros and cons of each approach?**

1. **`obj instanceof Object`**:
	* Pros: This approach checks for a specific prototype chain, which can be efficient for verifying that an object has a certain structure.
	* Cons: It may not be as straightforward or readable as other approaches, and it requires knowledge of JavaScript's prototype system.
2. **`obj.a === true`**:
	* Pros: This approach is simple and easy to read, but it relies on the specific value `true` being stored in property `a`. If this value changes, the test may fail unexpectedly.
	* Cons: It can be slower or more memory-intensive if the object `obj` has a large number of properties or if property `a` is accessed frequently.

**Other considerations**

* Both approaches assume that property `a` exists on object `obj`. If this property does not exist, the tests may fail unexpectedly.
* The tests do not account for the fact that `obj.a === true` will return `true` even if `a` is a number (e.g., 1) or another value that equals `true`.

**Library and special JS features**

There are no libraries used in this benchmark, but it does rely on JavaScript's built-in `Object` class.

**Special JS feature**

The test case uses the syntax `obj instanceof Object`, which relies on JavaScript's prototype system. This is a standard feature of JavaScript that allows you to check if an object has a certain prototype chain.

**Other alternatives**

Some alternative approaches to verify the existence or value of property `a` in object `obj` might include:

* Using a simple equality check like `obj.a === obj.a || (typeof obj.a !== 'undefined' && obj.a)`: This approach is more robust than just checking for `true`, but it may still be slower or less memory-efficient.
* Using a dedicated library like Lodash's `has` function: This approach can provide more flexibility and robustness, but it adds an additional dependency to the benchmark.

I hope this explanation helps! Let me know if you have any further questions.

Related benchmarks:

instanceof vs undefined prop (version: 0)

Comparing performance of: instanceof vs checking prop

Created: 4 years ago by: Guest

Jump to the latest result

instanceof

checking prop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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