Benchmark: Typeof x === 'undefined' vs x === undefined

Script Preparation code:

var x = undefined;

Tests:

Typeof check
typeof x === 'undefined';
Strict equality
x === 'undefined';

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Typeof check
Strict equality

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Overview**

The benchmark is testing two different approaches to compare a variable `x` with `'undefined'`. The first approach uses the `typeof` operator, while the second approach uses a strict equality check (`===`) with the string `'undefined'`.

**What are we comparing?**

We're comparing the performance of these two approaches:

1. **`typeof x === 'undefined'`**: This checks if the type of `x` is `'undefined'`. In JavaScript, `undefined` is a primitive value that represents an uninitialized or missing variable.
2. **`x === 'undefined'`**: This checks for strict equality between `x` and the string `'undefined'`.

**Pros and Cons**

**`typeof x === 'undefined'`:**

Pros:

* More concise and readable code
* Less chance of type coercion errors

Cons:

* May be slower due to additional type checking
* Requires a specific value (`undefined`) to work correctly

**`x === 'undefined'`:**

Pros:

* Faster performance, as it's a simple equality check
* Works with both primitive values and strings

Cons:

* More prone to type coercion errors if `x` is not a string
* Less readable code due to the need for explicit quotes around `'undefined'`

**Library usage**

There doesn't seem to be any external libraries used in this benchmark.

**Special JavaScript features or syntax**

The benchmark doesn't use any special JavaScript features or syntax beyond what's described above.

**Other alternatives**

If you wanted to compare these approaches, you might also consider using:

* `==` (loose equality) vs. `===` (strict equality)
* Using a different data type for `x`, such as a number or object
* Using a different JavaScript engine or implementation

Keep in mind that performance differences between these approaches can be influenced by many factors, including the specific use case, hardware, and optimization techniques used.

I hope this explanation helps!

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.82 Safari/537.36

Browser/OS: Chrome 89 on Windows

View result in a separate tab

Test name	Executions per second
Typeof check	13846839.0 Ops/sec
Strict equality	13878706.0 Ops/sec

Related benchmarks:

Typeof x === 'undefined' vs x === undefined (version: 0)

Comparing performance of: Typeof check vs Strict equality

Created: 4 years ago by: Guest

Jump to the latest result

Typeof check

Strict equality

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):