Benchmark: Array .push() vs .unshift() 2

Script Preparation code:

var arr = []; var arr2 = new Array(42);

Tests:

.unshift()
arr.unshift(42)
.push()
arr.push(42)
.push() preallocated array
arr2.push(42)
.unshift() preallocated array
arr2.unshift(42)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.unshift()
.push()
.push() preallocated array
.unshift() preallocated array

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36

Browser/OS: Chrome 68 on Windows

View result in a separate tab

Test name	Executions per second
.unshift()	16642.7 Ops/sec
.push()	6036818.5 Ops/sec
.push() preallocated array	5977727.0 Ops/sec
.unshift() preallocated array	32.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested.

**Benchmark Definition**

The benchmark definition json contains information about the test case, including:

* `Name`: The name of the test case, which is "Array .push() vs .unshift() 2".
* `Description`: No description is provided.
* `Script Preparation Code`: This code sets up two arrays, `arr` and `arr2`, with `arr2` being preallocated with a size of 42.

The script preparation code defines two variables:
	+ `var arr = [];` creates an empty array `arr`.
	+ `var arr2 = new Array(42);` creates an array `arr2` with a fixed size of 42, allocating memory in advance. This is done to compare the performance of `.push()` and `.unshift()` on preallocated vs non-preallocated arrays.

**Individual Test Cases**

The test cases are defined as an array of objects, each containing:

* `Benchmark Definition`: The actual JavaScript code being tested, such as `"arr.unshift(42)"`.
* `Test Name`: The name of the test case, which corresponds to the benchmark definition (e.g., ".unshift()").

Here's a brief explanation of each test case:

1. `.unshift()` on non-preallocated array (`arr`): Tests the performance of calling `.unshift()` on an empty array.
2. `.push()` on non-preallocated array (`arr`): Tests the performance of calling `.push()` on an empty array.
3. `.push()` on preallocated array (`arr2`): Tests the performance of calling `.push()` on a preallocated array with a fixed size.
4. `.unshift()` on preallocated array (`arr2`): Tests the performance of calling `.unshift()` on a preallocated array with a fixed size.

**Options Compared**

The test cases compare two options:

* Using an empty array (`arr`) vs using a preallocated array (`arr2`) when performing push or unshift operations.
* The impact of preallocating memory in advance (using `new Array(42)`) on performance.

**Pros and Cons**

Here are the pros and cons of each approach:

1. **Empty array (`arr`)**:
	* Pros: Simple, easy to set up, and allows for direct comparison with other test cases.
	* Cons: May incur additional overhead due to dynamic memory allocation.
2. **Preallocated array (`arr2`)**:
	* Pros: Reduces memory allocation overhead, as the size is fixed in advance.
	* Cons: Requires more setup code to create a preallocated array.

**Libraries and Special JS Features**

None of the test cases explicitly use any libraries or special JavaScript features. The script preparation code only uses built-in JavaScript constructs (arrays).

**Other Alternatives**

If you were to extend this benchmark, you might consider adding additional test cases to cover other aspects, such as:

* Using different array sizes or densities.
* Comparing performance with other methods like `concat()` or spread operators.
* Testing the impact of loop iteration on push/unshift performance.

Keep in mind that the specific design of the benchmark should aim to isolate the variable being tested (in this case, preallocating memory) while controlling for other variables that could affect performance.

Related benchmarks:

Array .push() vs .unshift() 2 (version: 0)

Comparing performance of: .unshift() vs .push() vs .push() preallocated array vs .unshift() preallocated array

Created: 6 years ago by: Guest

Jump to the latest result

.unshift()

.push()

.push() preallocated array

.unshift() preallocated array

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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