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.