Benchmark: Undefined testing

Script Preparation code:

var x;
var y = {};

Tests:

typeof x === "undefined"
typeof x === "undefined" typeof y === "undefined"
x === undefined
x === undefined y === undefined
x == undefined
x == undefined y == undefined
x == null
x == null y == null

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

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmarking data for you.

**Benchmark Overview**

The goal of this benchmark is to compare different ways to check if two variables (`x` and `y`) are "undefined" or "null". This test is essential in JavaScript development, as it can affect performance and code readability.

**Options Compared**

The benchmark tests the following options:

1. **typeof x === "undefined"`**: Checks if `x` is a variable with an undefined value.
2. **typeof y === "undefined"`**: Checks if `y` is an object (in this case, an empty object `{}`) with an undefined value.
3. **x === undefined`**: Checks for strict equality between `x` and the value `undefined`.
4. **y === undefined`**: Similar to option 2, but checks the value of `y` explicitly.
5. **x == null`**: Checks if `x` is a variable with a null value (although this is not exactly equivalent to "undefined" in JavaScript).
6. **x == undefined`**: Same as option 3.

**Pros and Cons**

Here's a brief analysis of each option:

* `typeof x === "undefined"`: This method can be misleading, as it also returns true for other types that are null or have been coerced to null (e.g., NaN). It's also slower due to the string comparison.
* `typeof y === "undefined"`: Similar to option 1, but checks an object instead of a variable. It's less intuitive than checking the value directly.
* `x === undefined` and `y === undefined`: These methods are more precise, as they perform strict equality checks with the value `undefined`. However, they might be slower due to the direct comparison.
* `x == null` and `x == undefined` (the same): This option is not recommended, as it doesn't accurately represent the JavaScript concept of "undefined".

**Library Usage**

The benchmark defines an empty object `y`, which seems to be used only for this test case. No external libraries are required or used.

**Special JS Features/Syntax**

None mentioned in the provided data.

**Other Alternatives**

To improve performance and accuracy, you might consider using more modern approaches, such as:

* Using the `isUndefined` function from Lodash (a popular utility library) for strict equality checks.
* Utilizing the `Object.is()` method (introduced in ECMAScript 2015) to check for object identity.

Keep in mind that these alternatives are not part of the standard JavaScript specification and may require additional setup or imports.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393

Browser/OS: Chrome 51 on Windows

View result in a separate tab

Test name	Executions per second
typeof x === "undefined"	74167584.0 Ops/sec
x === undefined	7531059.5 Ops/sec
x == undefined	7140890.5 Ops/sec
x == null	22071864.0 Ops/sec

Related benchmarks:

Undefined testing (version: 0)

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

Created: 7 years ago by: Guest

Jump to the latest result

typeof x === "undefined"

x === undefined

x == undefined

x == null

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):