Benchmark: Spread operator vs forEach

Script Preparation code:

var arr = [];
var count = 100000;
for (var i = 0; i < count; i++) {
  arr.push(i);
}

Tests:

Spread operator
var arr2 = [...arr];
forEach method
var arr2 = []; arr.forEach(x => arr2.push(x));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread operator
forEach method

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Linux

View result in a separate tab

Test name	Executions per second
Spread operator	5296.0 Ops/sec
forEach method	884.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark definition and test cases to explain what's being tested, compared, and other considerations.

**Benchmark Definition**

The benchmark definition is a JSON object that defines a JavaScript microbenchmark. It contains the following properties:

* `Name`: The name of the benchmark, which in this case is "Spread operator vs forEach".
* `Description`: An optional description of the benchmark, but it's empty in this case.
* `Script Preparation Code`: A script that sets up the environment before running the benchmark. In this case, it creates an array `arr` with 100,000 elements and pushes each element to the array.
* `Html Preparation Code`: An optional HTML code that can be used to prepare the test environment, but it's empty in this case.

**Test Cases**

The benchmark consists of two individual test cases:

1. "Spread operator":
	* The benchmark definition is `"var arr2 = [...arr];"`. This creates a new array `arr2` by spreading the elements of the original array `arr`.
	* The script preparation code remains the same as in the benchmark definition.
2. "forEach method":
	* The benchmark definition is `"var arr2 = [];\r\narr.forEach(x => arr2.push(x));"`. This creates a new array `arr2` by iterating over the elements of the original array `arr` using the `forEach` method and pushing each element to the new array.
	* The script preparation code remains the same as in the benchmark definition.

**What's being tested**

The two test cases are comparing the performance of the spread operator (`"[...arr]"`) versus the `forEach` method (`"arr.forEach(x => arr2.push(x))"`).

**Options compared**

The two options being compared are:

1. Spread operator: Creates a new array by spreading the elements of the original array.
2. `forEach` method: Iterates over the elements of the original array and pushes each element to a new array.

**Pros and Cons**

* Spread operator:
	+ Pros:
		- Creates a new array in a single operation, which can be more efficient for small arrays.
		- Can be more concise and readable than using `forEach`.
	+ Cons:
		- May create a new object on the heap if the original array contains objects, which can lead to memory issues.
		- Can be slower than using `forEach` for very large arrays.
* `forEach` method:
	+ Pros:
		- Can handle large arrays more efficiently since it only needs to iterate over each element once.
		- Does not create a new object on the heap, which can help with memory management.
	+ Cons:
		- Requires an extra iteration over the array elements, which can be slower than using the spread operator for small arrays.

**Library**

There is no explicit library mentioned in the benchmark definition. However, it's worth noting that some modern JavaScript environments may use optimized versions of `forEach` or other methods to improve performance.

**Special JS feature or syntax**

None are explicitly mentioned in this benchmark.

**Alternatives**

Some alternatives to the spread operator and `forEach` method include:

* Using `Array.prototype.map()` instead of the spread operator.
* Using a custom loop with an index variable instead of `forEach`.
* Using a library like Lodash's `_.map()` or `_.each()` for iteration.

However, these alternatives may not provide significant performance improvements over the original options being compared in this benchmark.

Related benchmarks:

Spread operator vs forEach (version: 0)

Comparing performance of: Spread operator vs forEach method

Created: 4 years ago by: Guest

Jump to the latest result

Spread operator

forEach method

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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