Benchmark: first test undeclared

Tests:

first case
var a 'a' in window 'b' in window
second case
var a window.hasOwnProperty('a') window.hasOwnProperty('b')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
first case
second case

Fastest: N/A

Slowest: N/A

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

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Let's dive into the world of MeasureThat.net and explore what's being tested in this benchmark.

**What is being tested?**

MeasureThat.net is testing the performance of JavaScript property access patterns, specifically the `in` operator versus the `hasOwnProperty` method. The benchmark compares how fast these two approaches are to check if a property exists on an object.

**Options compared:**

There are two main options being compared:

1. **`a ' in window`**: This approach uses the `in` operator, which checks if the specified string `'a'` is present as a property name in the `window` object.
2. **`window.hasOwnProperty('a')` and then `window.hasOwnProperty('b')`**: This approach first checks if `'a'` exists as an own property of the `window` object using `hasOwnProperty`, and only after that, it checks again for `'b'`.

**Pros and Cons:**

1. **`in` operator**:
	* Pros:
		+ Can be faster because it's a single operation.
	* Cons:
		+ May not always return the expected result if the property is inherited from a prototype chain.
		+ Some browsers may optimize this approach, making it slower in certain cases.
2. **`hasOwnProperty`**:
	* Pros:
		+ More accurate and reliable because it only checks own properties, skipping prototype chains.
	* Cons:
		+ May be slower due to the additional check.

**Library and purpose:**

There is no specific library mentioned in this benchmark, as both approaches rely on built-in JavaScript functionality. However, if we were to use a library like `fast-assert` or `assertjs`, they might provide more features for asserting property existence, but that's not the case here.

**Special JS feature or syntax:**

There are no special JavaScript features or syntax being used in this benchmark that would make it less accessible to a wide range of software engineers. The focus is on understanding the performance differences between two common property access patterns.

**Other alternatives:**

If you're interested in exploring more property access patterns, some other options could be:

* Using `Object.prototype.hasOwnProperty.call()` (or `hasOwnProperty` on non-prototype objects)
* Checking if a property exists using `in` with a try-catch block (`try { 'a' in obj } catch (e) { ... }`)
* Using libraries like `jsperf` or `benchmark.js` to compare performance of different approaches

However, for the purpose of this specific benchmark, comparing the `in` operator versus `hasOwnProperty` is sufficient.

Related benchmarks:

first test undeclared (version: 0)

Comparing performance of: first case vs second case

Created: 6 years ago by: Guest

Jump to the latest result

first case

second case

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):