Benchmark: array assignment vs array fill

Tests:

assign
const arr = [2,3,4,5,5,6,6,77,8]; let arr2 = []; arr2 = arr;
fill
const arr = [2,3,4,5,5,6,6,77,8]; let arr2 = []; arr2.push(...arr)
other assign
const arr = [2,3,4,5,5,6,6,77,8]; let arr2 = []; arr2 = [...arr];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
assign
fill
other assign

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/117.0.0.0 Safari/537.36

Browser/OS: Chrome 117 on Windows

View result in a separate tab

Test name	Executions per second
assign	828968320.0 Ops/sec
fill	30099638.0 Ops/sec
other assign	58156708.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the provided benchmark.

**Benchmark Overview**

The benchmark compares three different approaches to assign an array value to another array in JavaScript:

1. `arr2 = arr;` (Assignment by reference)
2. `arr2.push(...arr);` (Pushing elements from one array to another using spread syntax)
3. `arr2 = [...arr];` (Destructuring assignment, creating a new array)

**Options Compared**

The three approaches are compared in terms of performance, specifically:

* Execution speed: How quickly does each approach execute?
* Number of executions per second: A measure of the frequency with which each approach can be repeated.

**Pros and Cons of Each Approach**

1. **Assignment by reference (`arr2 = arr;`)**:
	* Pros: Simple and concise syntax.
	* Cons: Only assigns a reference to the original array, rather than creating a shallow copy. This means that both arrays will share the same underlying memory location.
	* Consideration: When working with mutable objects or arrays, this approach can lead to unexpected behavior if multiple variables are assigned references to the same object. However, when dealing with simple values like numbers or strings, it's likely sufficient.
2. **Pushing elements from one array to another using spread syntax (`arr2.push(...arr);`)**:
	* Pros: Creates a new array and copies all elements from the original array.
	* Cons: Can be slower than assignment by reference for small arrays due to the overhead of creating a new array.
	* Consideration: When working with large datasets, this approach can be more efficient than assignment by reference. However, it may not be suitable for very small arrays.
3. **Destructuring assignment (`arr2 = [...arr];`)**:
	* Pros: Creates a shallow copy of the original array and returns a new array.
	* Cons: Can be slower than assignment by reference due to the overhead of creating a new array.
	* Consideration: When working with complex data structures, this approach can be beneficial for preserving the integrity of the data.

**Library Used**

None of the provided benchmark definitions use any external libraries. The JavaScript code is self-contained and only relies on built-in functions and operators.

**Special JS Feature or Syntax**

The benchmark uses the spread syntax (`...`) introduced in ECMAScript 2015 (ES6) to create a new array. This feature allows for concise and expressive way of copying arrays or objects. The destructuring assignment syntax (`arr2 = [...arr];`) also relies on this feature.

**Other Alternatives**

Some alternative approaches could be considered:

* Using `Array.prototype.slice()` to create a shallow copy of the original array: `arr2 = arr.slice();`
* Using `Object.assign()` or `Array.prototype.push.apply()` to assign elements from one array to another
* Using libraries like Lodash or Ramda for more functional programming approaches

Keep in mind that these alternatives may have different performance characteristics and trade-offs depending on the specific use case.

Related benchmarks:

array assignment vs array fill (version: 0)

Comparing performance of: assign vs fill vs other assign

Created: 4 years ago by: Registered User

Jump to the latest result

assign

fill

other assign

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):