Benchmark: Array.prototype.concat vs spread operator

Tests:

slice
var other = [ "hello", true, 7 ].slice();
spread operator
var other = [ ...[ "hello", true, 7 ] ]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
spread operator

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided JSON and explain what's being tested.

The test is comparing two approaches to concatenate arrays in JavaScript:

1. **Traditional `concat()` method**: This involves using the built-in `concat()` function, which creates a new array by copying the contents of one or more source arrays.
2. **New ES6 spread operator (`...`)**: This allows you to use the spread operator to create a new array from an existing one.

**Pros and Cons:**

* Traditional `concat()` method:
	+ Pros: well-established, widely supported, and easy to understand.
	+ Cons: can be slower due to the creation of a new array, which involves copying the elements.
* New ES6 spread operator (`...`):
	+ Pros: efficient, modern, and expressive. Creates a shallow copy of the original array, avoiding unnecessary allocations.
	+ Cons: may not work as expected for more complex arrays or when dealing with non-array values.

**Other considerations:**

* **Memory allocation**: When using `concat()`, a new array is created, which can lead to increased memory usage and potentially slower performance. In contrast, the spread operator creates a shallow copy of the original array, reducing memory allocations.
* **Performance**: The spread operator generally outperforms `concat()` due to its optimized implementation under the hood.

**Library:**

There is no explicit library mentioned in this benchmark definition. However, it's worth noting that both approaches are built-in methods in JavaScript.

**Special JS feature/syntax:**

The use of the spread operator (`...`) is a relatively recent addition to the JavaScript language, introduced in ECMAScript 2015 (ES6). This syntax allows for more concise and expressive array manipulation.

Now, let's analyze the test results:

* The two tests measure the execution frequency per second (`ExecutionsPerSecond`) for each browser and device platform.
* The `slice()` test is faster than the spread operator test in both browsers, indicating that `concat()` might be optimized or more efficient for this particular use case.
* The `spread operator` test is faster in the Yandex Browser 17 but slower in the other browsers. This suggests that browser-specific optimizations or implementation differences play a role.

**Other alternatives:**

In addition to `concat()` and the spread operator, there are other approaches to concatenate arrays:

* **Array.prototype.push()**: Pushes elements onto the end of the array, which can be more efficient than creating a new array with `concat()` or the spread operator.
* **array.reduce()**: Uses the reduce method to concatenate elements, which can be less memory-intensive than creating an intermediate array.

These alternative approaches might provide different trade-offs between performance, memory usage, and code readability.

Related benchmarks:

Array.prototype.concat vs spread operator (version: 0)

Compare the new ES6 spread operator with the traditional concat() method

Comparing performance of: slice vs spread operator

Created: 8 years ago by: Guest

Jump to the latest result

slice

spread operator

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):