Benchmark: For vs While and Shift vs Array.slice

Script Preparation code:

var array = ["Rome", "Milan", "Barcelona", "Madrid", "Paris", "Nice", "London", "Manchester"];
var clone = [];

Tests:

Slice
clone = Array.prototype.slice.call(array, 0);
For
for(var i = 0; i < array.length; i++) { clone.push(array[i]); }
While
clone = Array.prototype.slice.call(array, 0); var clone2 = []; while(clone.length > 0) { clone2.push(clone.shift()); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice
For
While

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The provided benchmark compares three approaches to create a copy of an array: `Array.prototype.slice.call()`, `for` loop, and `while` loop with `shift()` method. The goal is to determine which approach is the fastest.

**Options Compared**

1. **`Array.prototype.slice.call()`**: This method creates a new array by calling the `slice()` method on the original array and passing `0` as the start index.
2. **`for` loop**: This loop iterates over the elements of the original array using an indexer (`i`) and pushes each element to a new array (`clone`).
3. **`while` loop with `shift()` method**: This loop uses a while loop to iterate over the elements of the original array, pushing each element to a new array (`clone2`) using the `shift()` method.

**Pros and Cons**

1. **`Array.prototype.slice.call()`**:
	* Pros: Creates a shallow copy of the array, easy to read and write.
	* Cons: Can be slower than other approaches for large arrays due to the overhead of creating an array object.
2. **`for` loop**:
	* Pros: Can be more efficient for large arrays since it avoids the overhead of creating an array object.
	* Cons: Requires manual indexing, which can lead to errors if not implemented correctly.
3. **`while` loop with `shift()` method**:
	* Pros: More memory-efficient than other approaches since it uses a single array and doesn't create a new object.
	* Cons: Can be slower due to the overhead of iterating over the elements using `shift()`, which returns the first element.

**Library**

None, this benchmark only uses built-in JavaScript features.

**Special JS Feature/Syntax**

The `shift()` method is used in the `while` loop approach. The `shift()` method returns the first element of an array and removes it from the array. This approach relies on this method to iterate over the elements.

**Benchmark Preparation Code**

The provided code initializes two arrays: `array` containing city names, and `clone`/`clone2` which will hold the copied values.

**Individual Test Cases**

Each test case measures the execution time of a specific approach:

1. **Slice**: Creates a copy using `Array.prototype.slice.call()`.
2. **For**: Uses a `for` loop to create a copy.
3. **While**: Uses a `while` loop with `shift()` method to create a copy.

**Benchmark Result**

The latest benchmark result shows the execution time per second for each test case on a Chrome 95 browser on a Mac OS X 10.15.7 desktop platform:

1. **Slice**: 3,326,201 executions/second
2. **While**: 6,681,716 executions/second
3. **For**: 6,107,630 executions/second

Based on the benchmark results, the `while` loop approach appears to be the fastest.

**Other Alternatives**

If you're interested in exploring alternative approaches, here are a few options:

1. **Using `Array.prototype.map()`**: This method creates a new array by calling the `map()` method on the original array.
2. **Using `Object.assign()`**: This method creates a new object by copying the properties of the original object.
3. **Using `Array.from()`**: This method creates a new array from an iterable object.

Keep in mind that each approach has its pros and cons, and the best choice depends on your specific use case and performance requirements.

Related benchmarks:

For vs While and Shift vs Array.slice (version: 1)

Comparing performance of: Slice vs For vs While

Created: 4 years ago by: Registered User

Jump to the latest result

Slice

For

While

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):