Benchmark: Test the speed of typeof vs. constructor

Script Preparation code:

function func() { console.log('Hello world!') }

Tests:

typeof
typeof func === 'function'
constructor
func.constructor === Function

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof
constructor

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
typeof	170980096.0 Ops/sec
constructor	162880208.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**What is being tested?**

The provided JSON represents two individual test cases for measuring the performance difference between `typeof` and `constructor` when used to check if a variable is a function. In essence, the tests are designed to compare the speed of two approaches:

1. Using `typeof` (e.g., `typeof func === 'function'`)
2. Using `constructor` (e.g., `func.constructor === Function`)

**Options being compared:**

The options being compared are essentially two different ways to check if a variable is a function.

* **Option 1: `typeof`**
	+ The `typeof` operator returns a string indicating the type of its operand. In this case, it will return `'function'` for an object that is a function.
	+ Pros:
		- Simple and straightforward syntax.
		- Wide support across different browsers and JavaScript engines.
	+ Cons:
		- May be slower due to the need to resolve the type string from the `typeof` internal lookup table, which can lead to a performance overhead.
* **Option 2: `constructor`**
	+ The `constructor` property of an object returns its constructor function. In this case, it will return the `Function` constructor for a variable that is a function.
	+ Pros:
		- Can be faster than `typeof`, as it doesn't require resolving a type string from an internal lookup table.
	+ Cons:
		- May not work correctly with non-constructor objects (e.g., primitive values).
		- Less straightforward syntax.

**Other considerations:**

While the tests only compare these two specific approaches, there are other factors to consider when writing JavaScript performance benchmarks:

*   **Library usage:** In this benchmark, no libraries are used. However, when testing complex algorithms or large datasets, using libraries like Lodash can significantly impact the results.
*   **Special JS features or syntax:** This benchmark doesn't mention any special JavaScript features or syntax that could affect the test results. If it did, we would need to take those into account.

**Alternatives:**

If you're interested in exploring alternative approaches or optimizations for this specific use case:

*   **Checking `Object.prototype.toString.call(func)`**: Instead of using `typeof` or `constructor`, some developers might opt for checking the result of `Object.prototype.toString.call(func)`. This approach can be faster but may require additional checks to ensure it works correctly.
*   **Using a custom function check**: You could create a custom function that checks if an object is a function and compare its performance with `typeof` or `constructor`.

In conclusion, this benchmark compares the performance of two approaches for checking if a variable is a function: using `typeof` versus `constructor`. While both have their pros and cons, it's essential to consider additional factors like library usage and special JavaScript features when writing performance benchmarks.

Related benchmarks:

Test the speed of typeof vs. constructor (version: 0)

Comparing performance of: typeof vs constructor

Created: 6 years ago by: Guest

Jump to the latest result

typeof

constructor

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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