Benchmark: void 0 vs undefined

Script Preparation code:

var k = new Array(10000);

Tests:

undefined
k.fill(undefined);
void 0
k.fill(void 0);

Historical Performance Data aggregated from 14 community runs

Desktop Results:

Chrome 14 runs

void 0

88K/s

undefined

87K/s

View exact numbers

✓ void 0: 88,366 ops/sec
• undefined: 87,482 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
void 0

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/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Windows

View result in a separate tab

undefined

37K/s

void 0

36K/s

View exact numbers

Test name	Executions per second
✓ undefined	37,150 Ops/sec
void 0	35,680 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark definition and test cases to explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**
The benchmark definition is a JSON object that contains information about the test case. Here's a breakdown of its components:

* **Name**: The name of the benchmark.
* **Description**: An optional description of the benchmark (in this case, null).
* **Script Preparation Code**: A script that must be run before each test case to prepare the environment. In this case, it creates an array `k` with 10,000 elements and assigns a value to it using `new Array(10000);`. However, there's no JavaScript assignment operator (`=`) in the code, which is unusual for benchmarking purposes.
* **Html Preparation Code**: An optional script that must be run before each test case to prepare the HTML environment (in this case, null).

**Test Cases**
The benchmark definition contains two individual test cases:

1. **"undefined"**
	* **Benchmark Definition**: `k.fill(undefined);`
	* This line of code fills the array `k` with the value `undefined`.
2. **"void 0"**
	* **Benchmark Definition**: `k.fill(void 0);`
	* This line of code fills the array `k` with the value `0`.

**Comparison**
The two test cases are comparing the performance difference between using `undefined` and `void 0` when filling an array.

**Pros and Cons**

* **Using `undefined`:**
	+ Pros:
		- Can be more intuitive for developers, as it clearly conveys the intention of setting a value to "no value" or "no property".
	+ Cons:
		- In some older JavaScript engines or browsers, `undefined` is not a valid argument for `fill()` (it's only supported in ECMAScript 5 and later).
* **Using `void 0`:**
	+ Pros:
		- It's a more explicit way to set the value to "no value" or "no property", as it explicitly uses the `void` keyword followed by `0`.
	+ Cons:
		- May be less intuitive for some developers, especially those who are not familiar with the `void` operator.

**Other Considerations**

* The use of `new Array(10000);` in the script preparation code is unusual and might not be relevant to the benchmarking of `fill()`.
* There's no indication that either `undefined` or `void 0` should have any significant performance difference, as both values are essentially "no value" when used with `fill()`.

**Library**
There doesn't seem to be a specific library being used in these benchmark test cases. The code is standard JavaScript, and the only external resource mentioned is the browser's user agent string (`RawUAString`) in the benchmark result.

**Special JS Features or Syntax**
None of the provided code snippet uses any special JavaScript features or syntax that would require additional explanation.

void 0 vs undefined (version: 0)

Comparing performance of: `undefined vs void 0`

Created: 4 years ago by: Guest

Go to the latest result

undefined

void 0

Historical Performance Data aggregated from 14 community runs

Desktop Results:

Chrome 14 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

void 0 vs undefined (version: 0)

Comparing performance of: undefined vs void 0

Created: 4 years ago by: Guest

Go to the latest result

undefined

void 0

Historical Performance Data aggregated from 14 community runs

Desktop Results:

Chrome 14 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `undefined vs void 0`