Benchmark: Undefined testing

Script Preparation code:

var x;
var y = {};

Tests:

typeof x === "undefined"
typeof x === "undefined"
x === undefined
x === undefined

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof x === "undefined"
x === undefined

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its options.

**Benchmark Definition**

The benchmark is defined by two scripts: one for preparing the test environment (`Script Preparation Code`) and another empty string (`Html Preparation Code`). The purpose of these scripts seems to be minimal, only setting up a variable `x` as undefined.

**Options Compared**

There are two options being compared:

1. `typeof x === "undefined"`
2. `x === undefined`

Both expressions check if `x` is undefined, but they do so in different ways.

**Pros and Cons**

* **`typeof x === "undefined"`**
	+ Pros:
		- More concise and readable.
		- Less vulnerable to type coercion issues (e.g., `null` and `undefined` are treated as distinct values).
	+ Cons:
		- May not be optimized by the JavaScript engine, which might lead to a performance hit compared to the second option.
* **`x === undefined`**
	+ Pros:
		- Might be more efficient due to potential optimizations in the JavaScript engine.
	+ Cons:
		- Less readable and more prone to type coercion issues.

**Library**

There is no library explicitly mentioned in this benchmark. However, it's worth noting that some modern JavaScript engines might use techniques like "opt-in" or "opt-out" optimization for `typeof` checks, which could affect the performance of these expressions.

**Special JS Feature/Syntax**

None are explicitly mentioned in this benchmark. However, if you were to add any special features or syntax (e.g., ES6+ classes, async/await), it would impact how the test is executed and interpreted by the JavaScript engine.

**Other Alternatives**

If you wanted to explore alternative approaches, here are a few:

* Using `x == undefined` instead of `typeof x === "undefined"`.
* Adding additional checks for specific values (e.g., `x == null`, `x == undefined || x == null`).
* Comparing the execution time of different libraries or frameworks that implement JavaScript engine optimizations.
* Investigating how other programming languages or runtimes handle similar checks.

Keep in mind that altering these tests could significantly impact their accuracy and reliability, so it's essential to understand the underlying assumptions and potential pitfalls.

Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36 OPR/41.0.2353.69

Browser/OS: Opera 41 on Windows

View result in a separate tab

Test name	Executions per second
typeof x === "undefined"	7456273.5 Ops/sec
x === undefined	2807675.0 Ops/sec

Related benchmarks:

Undefined testing (version: 0)

Comparing performance of: typeof x === "undefined" vs x === undefined

Created: 7 years ago by: Guest

Jump to the latest result

typeof x === "undefined"

x === undefined

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):