Benchmark: Undefined testing including !

Script Preparation code:

var x;

Tests:

typeof x === "undefined"
typeof x === "undefined"
x === undefined
x === undefined
x == undefined
x == undefined
x == null
x == null
!x
!x

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36 OPR/102.0.0.0

Browser/OS: Opera 102 on Windows

View result in a separate tab

Test name	Executions per second
typeof x === "undefined"	13208726.0 Ops/sec
x === undefined	4919502.0 Ops/sec
x == undefined	4981227.5 Ops/sec
x == null	13932452.0 Ops/sec
!x	13954638.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, the options compared, their pros and cons, and other considerations.

**Benchmark Overview**

The benchmark measures the performance of JavaScript in determining if a variable `x` is undefined or null. The test cases compare different approaches to check for `undefined` or `null`.

**Script Preparation Code**
```javascript
var x;
```
This line declares a global variable `x` with no initial value, making it `undefined` by default.

**Html Preparation Code**

There is no HTML preparation code provided, which means that the benchmark is running on a minimal JavaScript engine without any additional overhead from HTML parsing or rendering.

**Test Cases**

The test cases compare the performance of different approaches to check if `x` is `undefined`, `null`, or not equal to `undefined` (using `!==`). The options compared are:

1. **typeof x === "undefined"`: Checks the type of `x` using the `typeof` operator and compares it to `"undefined"`.
2. **x === undefined**: Directly compares `x` with `undefined` using the equality operator (`===`).
3. **x == undefined**: Uses a loose comparison operator (`==`) instead of the strict comparison operator (`===`). This can lead to different results due to type coercion.
4. **x == null**: Checks if `x` is equal to `null` using the same loose comparison operator (`==`).
5. **!x**: Uses the logical NOT operator (`!`) to negate the value of `x`, effectively checking if it's not undefined or null.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **typeof x === "undefined"`:
	* Pros: This approach is more explicit and clearly communicates the intention to check for `undefined`.
	* Cons: It may lead to slower performance due to the additional type checking.
2. **x === undefined**:
	* Pros: This approach is simple and directly checks for equality with `undefined`.
	* Cons: It can lead to unexpected results if `x` is not exactly equal to `undefined`, but rather close to it (e.g., due to floating-point precision issues).
3. **x == undefined**:
	* Pros: This approach uses a loose comparison operator, which can lead to faster performance by allowing type coercion.
	* Cons: It may produce unexpected results due to type coercion and should be avoided in production code.
4. **x == null**:
	* Pros: This approach is similar to the previous one but checks for `null` specifically.
	* Cons: It's still using a loose comparison operator, which can lead to issues with non-null values being treated as equal to `null`.
5. **!x**:
	* Pros: This approach uses the logical NOT operator, which can be more efficient than direct equality comparisons.
	* Cons: It may not clearly convey the intention to check for `undefined` or `null`, making it less readable.

**Library and Special Features**

There are no libraries explicitly mentioned in the benchmark definition. However, some test cases use features like the logical NOT operator (`!`) and the loose comparison operators (`==`).

**Other Considerations**

Some additional considerations when working with JavaScript:

* When using `typeof x === "undefined"`, be aware that it may lead to slower performance due to type checking.
* Always use the strict comparison operator (`===`) instead of the loose comparison operator (`==`) unless explicitly intended for type coercion.
* Be cautious when working with floating-point values, as they can lead to unexpected results in comparisons.

**Alternatives**

If you're looking for alternative approaches or ways to optimize these tests, consider:

* Using a more efficient data structure, like a `Set` or an array, instead of a single variable `x`.
* Implementing a custom comparison function that uses the `===` operator and is optimized for performance.
* Utilizing modern JavaScript features like `optional chaining` (`?.`) or `nullish coalescing` (`??`) to simplify your checks.

Related benchmarks:

Undefined testing including ! (version: 0)

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

Created: one year ago by: Guest

Jump to the latest result

typeof x === "undefined"

x === undefined

x == undefined

x == null

!x

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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