Overview

The provided benchmark, hosted on MeasureThat.net, compares three approaches for appending elements to a large array in JavaScript: push(), concat(), and the spread operator (...). The test aims to determine which approach is faster and more efficient.

Options Compared

1. push(): This method modifies the array by adding one or more elements to the end of it.
2. concat(): This method returns a new array that contains all elements from the original array, followed by the elements passed as an argument (in this case, window.test).
3. Spread Operator (...): This operator creates a new array with the elements of the original array and the elements passed as an argument.

Pros and Cons

1. push():
   • Pros: Fastest and most efficient way to append elements to an array.
   • Cons: Modifies the original array, which might be undesirable in some cases.
2. concat():
   • Pros: Returns a new array, preserving the original array's integrity.
   • Cons: Slower than push(), as it creates a new array and copies all elements from the original array.
3. Spread Operator (...):
   • Pros: Creates a new array without modifying the original array.
   • Cons: Can be slower than push() due to the overhead of creating a new array.

Library Usage

None of the test cases use external libraries, which is good for isolating the JavaScript engine's behavior and reducing potential interference from library-side optimizations or invariants.

Special JS Features/Syntax

The test does not utilize any special JavaScript features or syntax beyond what is necessary to demonstrate the three approaches. If additional features were used, it would require more context about their implementation and how they affect performance.

Alternative Approaches

1. Array.prototype.reduce(): This method reduces an array by applying a callback function to each element, accumulating a result. While not directly comparable to push() or concat(), it can be used as an alternative way to append elements to an array.
2. Array.prototype.map(): Similar to reduce(), this method creates a new array with the results of applying a provided function to each element in the original array. Again, not directly comparable to push() or concat().
3. Native WebAssembly (WASM): If you need extreme performance, you could consider using native WASM code, which can be compiled to run on the JavaScript engine's optimized backend. However, this would require more complex setup and might not be necessary for most use cases.

Keep in mind that these alternative approaches have different use cases and performance characteristics compared to push(), concat(), and the spread operator.