Benchmark: Array spread clone vs manual clone

Script Preparation code:

var arr = [];
for (let i = 0; i < 10000000; ++i) {
	arr.push(i);
}

Tests:

spread operator
let cloned = [...arr];
manual clone
let cloned = new Array(arr.length); for (let i = 0; i < arr.length; ++i) { cloned[i] = arr[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread operator
manual clone

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided benchmark definition and test cases.

**What is tested?**

The provided JSON represents a JavaScript microbenchmark that compares two approaches to cloning an array:

1. **Spread Operator (`[...arr]`)**: This method creates a new array by iterating over the elements of the original array.
2. **Manual Clone**: This method creates a new array with the same length as the original array and then populates it with the values from the original array using indexing.

**Options compared**

The benchmark compares these two approaches to cloning an array:

* Spread Operator (`[...arr]`)
* Manual Clone (using `new Array(arr.length)` and indexing)

**Pros and Cons of each approach:**

1. **Spread Operator (`[...arr]`)**:
	* Pros:
		+ Concise and expressive syntax
		+ Can handle arrays with nested objects or other complex data structures
		+ May be faster due to the optimized V8 engine implementation
	* Cons:
		+ Can be slower for very large arrays due to the overhead of creating a new array
		+ Not supported in older browsers (e.g., Internet Explorer)
2. **Manual Clone**:
	* Pros:
		+ More control over the cloning process
		+ Suitable for custom data structures or edge cases
		+ May be faster for very large arrays due to direct indexing
	* Cons:
		+ Longer syntax, which can make it harder to read and maintain
		+ Requires manual handling of array length and indexing

**Other considerations:**

When choosing between these approaches, consider the specific use case and performance requirements. If you need a concise and expressive way to clone arrays with complex data structures, the spread operator might be a better choice. However, if you require fine-grained control over the cloning process or work with very large arrays, manual cloning might be more suitable.

**Library**

There is no library explicitly mentioned in this benchmark definition. However, the V8 JavaScript engine (used by Chrome and other browsers) has optimized implementations of the spread operator for performance.

**Special JS feature/syntax**

The benchmark uses the spread operator (`[...arr]`), which is a modern JavaScript syntax introduced in ECMAScript 2015 (ES6). It allows for concise array creation using the `...` operator, which spreads elements from an iterable into a new array. This syntax is widely supported by modern browsers and engines.

**Alternatives**

Other alternatives to these approaches include:

1. **Array.prototype.slice()**: Creates a shallow copy of the original array.
2. **Array.prototype.concat()**: Combines one or more arrays (or array-like objects) into a new array.
3. **JSON.parse(JSON.stringify(arr))**: Creates a deep copy of the original array using JSON serialization.

Each alternative has its pros and cons, and the choice depends on the specific use case and requirements.

Related benchmarks:

Array spread clone vs manual clone (version: 0)

Comparing performance of: spread operator vs manual clone

Created: 2 years ago by: Guest

Jump to the latest result

spread operator

manual clone

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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