Benchmark: Array slice vs for loop output

Script Preparation code:

var data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];

Tests:

slice then for... of
var copy = data.slice(3, 8); for (var item of copy) { console.log('item ${item}'); }
for loop
var copy = []; for (var i = 3; i < 8; i++) { console.log('item ${item}'); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice then for... of
for loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36

Browser/OS: Chrome 117 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
slice then for... of	87077.0 Ops/sec
for loop	93300.9 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and explain what's being tested, compared options, pros and cons, and other considerations.

**What is being tested?**

The benchmark compares two approaches to achieve a specific output:

1. Using `Array.prototype.slice()` to create a subset of an array (`"slice then for... of"` test case).
2. Using a traditional `for` loop to iterate over a portion of the array (`"for loop"` test case).

**What is the purpose of each approach?**

* The `slice()` method returns a new array containing the elements from the original array, starting from the specified start index (3 in this case) and ending at the specified end index (8 in this case).
* The traditional `for` loop iterates over the specified range of indices using a variable `i`.

**Options compared**

The benchmark compares two options:

1. **Using `Array.prototype.slice()`**: This approach is more concise and readable, but it creates a new array and may have performance implications.
2. **Traditional `for` loop**: This approach is more verbose but can be optimized for performance.

**Pros and Cons of each approach**

* **Using `Array.prototype.slice()`:**
	+ Pros:
		- More concise and readable code
		- Creates a new array, which might not affect the original array's performance
	+ Cons:
		- Creates a new array object, which may incur memory allocation overhead
		- May be slower due to the creation of a new array object
* **Traditional `for` loop:**
	+ Pros:
		- More control over the iteration process
		- Can be optimized for performance using techniques like caching or memoization
	+ Cons:
		- More verbose code, making it less readable
		- May require more manual memory management

**Library and special JS features**

The benchmark uses the `console` object from the browser's global scope. The `for...of` loop syntax is a modern JavaScript feature introduced in ECMAScript 2015 (ES6) as part of the `for...of` loop iteration pattern.

**Other considerations**

* Memory allocation: Both approaches create a new array or use existing variables, but the traditional `for` loop might be more memory-efficient due to the reuse of local variables.
* Cache performance: The traditional `for` loop can potentially benefit from cache-friendly access patterns, whereas the `slice()` method may incur additional overhead due to the creation of a new array object.

**Alternatives**

If you're looking for alternative approaches, consider:

1. **Using `Array.prototype.subarray()`**: This method returns a shallow copy of a specified portion of an array, similar to `slice()`. However, it might be more suitable for subarrays that need to preserve the original array's structure.
2. **Iterating over the array using `forEach()` or `map()`**: These methods provide an alternative way to iterate over arrays without creating a new array object.
3. **Using `WeakMap` or other data structures**: Depending on your specific use case, you might find more efficient solutions by using specialized data structures like `WeakMap`, `Set`, or others.

Keep in mind that the optimal approach depends on the specific requirements and constraints of your project.

Related benchmarks:

Array slice vs for loop output (version: 0)

Comparing performance of: slice then for... of vs for loop

Created: one year ago by: Guest

Jump to the latest result

slice then for... of

for loop

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):