Benchmark: Spread vs push array

Script Preparation code:

var f = [1,2,3]
var l = [4,5]

Tests:

push spreader
f.push(...l)
spread itself
f = [...f, ...l]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
push spreader
spread itself

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; rv:109.0) Gecko/20100101 Firefox/111.0

Browser/OS: Firefox 111 on Windows

View result in a separate tab

Test name	Executions per second
push spreader	6692193.0 Ops/sec
spread itself	0.4 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in this benchmark.

**Benchmark Overview**

The benchmark compares two ways of adding elements to an array: using the `push` method with the spread operator (`...`) and using the spread operator on its own.

**Options Compared**

There are two main options being compared:

1. **`f.push(...l)`**: This option uses the spread operator (`...`) to add all elements from the `l` array to the end of the `f` array using the `push` method.
2. **`f = [...f, ...l]`**: This option creates a new array by concatenating the current `f` array with the spread operator applied to both `f` and `l`.

**Pros and Cons**

* **`f.push(...l)`**:
	+ Pros: This method is more concise and readable. It avoids creating an intermediate array, which can be beneficial for large datasets.
	+ Cons: In older browsers (e.g., Internet Explorer), the spread operator is not supported. Also, it may lead to slower performance due to the overhead of the `push` method.
* **`f = [...f, ...l]`**:
	+ Pros: This method creates a new array, which can be beneficial for large datasets as it avoids modifying the original array. It's also more explicit and easier to understand.
	+ Cons: This method is less concise and may lead to slower performance due to the creation of an intermediate array.

**Library Usage**

There doesn't appear to be any specific library usage in this benchmark. However, modern JavaScript engines (like Firefox) support the spread operator, which is a part of the ECMAScript 2015 standard.

**Special JS Feature or Syntax**

The use of the spread operator (`...`) and template literals (`\r\nvar f = [1,2,3]\r\nvar l = [4,5]`) is specific to modern JavaScript engines. Older browsers may not support these features.

**Other Alternatives**

If `push` with spread operator or spread operator on its own isn't suitable for your use case, you could consider other methods:

* Using the `concat` method: `f.concat(l)`
* Creating a new array using the `Array.prototype.map` method: `[...l].map(x => f.push(x))`
* Using a library like Lodash's `unionBy` function

However, these alternatives may have performance implications and might not be as concise or readable as the options being compared in this benchmark.

Related benchmarks:

Spread vs push array (version: 0)

Comparing performance of: push spreader vs spread itself

Created: 2 years ago by: Guest

Jump to the latest result

push spreader

spread itself

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):