Benchmark: Array assign vs spread operator vs push

Tests:

Spread operator
var x = [] for(var i = 0; i < 60000; i++) { x = [...x, i] } return x
Assign
var x = [] for(var i = 0; i < 60000; i++) { x[i] = i } return x
Push
var x = [] for(var i = 0; i < 60000; i++) { x.push(i) } return x

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread operator
Assign
Push

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Browser/OS: Chrome 86 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
Spread operator	0.2 Ops/sec
Assign	2067.5 Ops/sec
Push	1986.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark JSON and explain what's being tested, compared, and their pros and cons.

The benchmark is designed to compare the performance of three ways to create or append elements to an array:

1. **Spread operator (`...`)**: This syntax creates a new array by spreading the existing array `x`.
2. **Assignment (`=`)**: Assigning a value to each index of the array `x`.
3. **Push**: Using the `push()` method to add elements to the end of the array `x`.

**What's being tested?**

The benchmark is testing how fast these three approaches are for creating an array of 60,000 elements.

**Options comparison:**

Here's a brief overview of each approach:

* **Spread operator (`...`)**:
	+ Pros:
		- Creates a new array, which can be more efficient than modifying an existing one.
		- Allows for concise code and is often preferred in modern JavaScript development.
	+ Cons:
		- May create a temporary array object, leading to higher memory allocation and garbage collection overhead.
* **Assignment (`=`)**:
	+ Pros:
		- Modifies the existing array `x`, avoiding the creation of a new array.
	+ Cons:
		- Can lead to slower performance due to frequent index assignments.
		- May cause issues if not handled carefully, as it can result in an empty or unexpected array.
* **Push**:
	+ Pros:
		- Modifies the existing array `x` efficiently, adding elements to its end without creating a new array.
	+ Cons:
		- Requires access to the array's length property and can lead to slower performance if not handled carefully.

**Other considerations:**

* Memory allocation and garbage collection: The spread operator may incur more memory overhead due to the creation of a temporary array object, while assignment and push operations are generally more efficient in terms of memory management.
* Cache locality: The push operation is likely to have better cache locality than the other two options, as it modifies the existing array's end element without needing to access intermediate elements.

**Library usage:**

There doesn't appear to be any explicit library usage mentioned in the benchmark definition or test cases. However, the benchmark may rely on internal browser libraries for its performance measurements and execution.

**Special JS features:**

The benchmark uses modern JavaScript syntax, including the spread operator (`...`), which is a relatively recent addition to the language (introduced in ECMAScript 2018).

**Alternatives:**

To further improve or modify this benchmark, alternative approaches could be explored, such as:

* Using `Array.prototype.reduce()` for the spread operator
* Employing a custom implementation of the assignment and push operations
* Adding more test cases with varying array sizes and types (e.g., objects)
* Incorporating additional performance metrics, like memory allocation or CPU utilization

Related benchmarks:

Array assign vs spread operator vs push (version: 1)

Comparing performance of: Spread operator vs Assign vs Push

Created: 4 years ago by: Registered User

Jump to the latest result

Spread operator

Assign

Push

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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