Benchmark: hasOwnProperty vs direct access (bool) vs in

Script Preparation code:

var x = { a: 1, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8, i: 9}

Tests:

hasOwnProperty
x.hasOwnProperty("a")
direct access (bool)
x["a"]
in
"a" in x

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
hasOwnProperty
direct access (bool)
in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36 Edg/131.0.0.0

Browser/OS: Chrome 131 on Windows

View result in a separate tab

Test name	Executions per second
hasOwnProperty	64563732.0 Ops/sec
direct access (bool)	158996544.0 Ops/sec
in	162691312.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 7 months ago):

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in this JavaScript microbenchmark.

**Benchmark Description**

The benchmark is designed to compare the performance of three different ways to access an object property:

1. `x.hasOwnProperty("a")`: This uses the `hasOwnProperty` method, which checks if a property exists on the object.
2. `x["a"]`: This uses direct property access, where you access the property using square brackets `[]`.
3. `"a" in x`: This uses the "in" operator to check if a property exists on the object.

**Options Compared**

The benchmark compares the performance of these three options:

* **hasOwnProperty**: Checks if a property exists on the object using the `hasOwnProperty` method.
* **Direct Access (bool)**: Uses direct property access, where you access the property using square brackets `[]`.
* **in**: Uses the "in" operator to check if a property exists on the object.

**Pros and Cons**

Here are some pros and cons of each approach:

* **hasOwnProperty**:
	+ Pros: More explicit and safe way to check for properties, especially in cases where you're not sure what properties exist.
	+ Cons: Can be slower than direct access or "in" because it involves a method call.
* **Direct Access (bool)**:
	+ Pros: Faster and more efficient because it doesn't involve a method call or an operator.
	+ Cons: Less explicit and may lead to errors if the property does not exist.
* **in**:
	+ Pros: Fast and efficient, but can be ambiguous in cases where the property is defined on both the object itself and its prototype chain.
	+ Cons: Less safe than `hasOwnProperty` because it doesn't guarantee that the property exists only on the current object.

**Library and Special JS Features**

None of these options rely on any specific library or special JavaScript feature. They are basic language constructs that are widely supported across most browsers and environments.

**Considerations**

When choosing between these approaches, consider the trade-offs between performance, safety, and explicitness:

* If you need to ensure that a property exists only on the current object, use `hasOwnProperty`.
* If you're sure that the property exists and just want to access it efficiently, use direct access or "in".
* If you're unsure about the properties defined on an object and want to avoid errors, use `hasOwnProperty`.

**Alternatives**

Other alternatives for accessing object properties include:

* Using a library like Lodash's `_.has` function.
* Using a utility function that checks if a property exists and provides a fallback value if it doesn't.
* Using a more modern JavaScript feature like optional chaining (`?.`) or the nullish coalescing operator (`??`) to access properties in a safe and efficient way.

Keep in mind that these alternatives may introduce additional dependencies, complexity, or overhead, so consider your specific use case and requirements before choosing an alternative.

Related benchmarks:

hasOwnProperty vs direct access (bool) vs in (version: 0)

Comparing performance of: hasOwnProperty vs direct access (bool) vs in

Created: 3 years ago by: Guest

Jump to the latest result

hasOwnProperty

direct access (bool)

in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 7 months ago):