Benchmark: Array.from vs spread vs construct manually

Script Preparation code:

var src = Object.keys([...Array(10000)]);
var z = {};

Tests:

Array.from
z.z = Array.from(src[Symbol.iterator]());
manual
let n = src.length; let a = Array(n); let iter = src[Symbol.iterator](); for (let i = 0; i < n; ++i) {a[i] = iter.next().value;}; z.z = a;
spread
z.z = [...(src[Symbol.iterator]())];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.from
manual
spread

Fastest: N/A

Slowest: N/A

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

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Let's dive into explaining the provided JSON benchmark.

**Benchmark Purpose:**
The purpose of this benchmark is to compare three approaches for creating an array from a large dataset:

1. Using `Array.from()`
2. Spreading an iterator manually
3. Constructing the array manually using a loop

These approaches are compared in terms of their performance, measured by the number of executions per second.

**Options Compared:**

* **`Array.from()`**: A built-in JavaScript method that creates a new array from an iterable (e.g., an iterator) or an array-like object.
* **Spreading an iterator manually**: This involves using the spread operator (`...`) to create a new array by iterating over an existing array or iterator.
* **Constructing the array manually**: This approach uses a loop to push elements onto a new array.

**Pros and Cons:**

* **`Array.from()`**:
	+ Pros: concise, readable, and efficient for most use cases.
	+ Cons: may incur overhead due to its built-in nature, potentially slower than manual approaches for very large datasets.
* **Spreading an iterator manually**:
	+ Pros: allows for more control over the iteration process, can be faster for large datasets.
	+ Cons: less readable and maintainable than `Array.from()`, may require additional code to handle edge cases.
* **Constructing the array manually**:
	+ Pros: provides complete control over the iteration process, can be the fastest approach for very large datasets.
	+ Cons: verbose, error-prone, and less readable.

**Library/Functionality:**
In this benchmark, the `Symbol.iterator` method is used to create an iterator from the original array. This allows us to iterate over the elements of the array without creating a temporary copy.

**Special JavaScript Feature/Syntax:**
The use of `Spread operator (`...`) and `Symbol.iterator` are standard features in modern JavaScript. The spread operator is used to create a new array by iterating over an existing array or iterator, while `Symbol.iterator` allows us to define custom iteration protocols for objects.

**Other Alternatives:**
If you need to create an array from a large dataset, other approaches might include:

* Using `Array.prototype.slice()` or `Array.prototype.concat()`
* Utilizing libraries like Lodash or Ramda
* Employing parallel processing techniques using web workers or other concurrency models

Keep in mind that the best approach depends on your specific use case, performance requirements, and personal preference.

Related benchmarks:

Array.from vs spread vs construct manually (version: 0)

Comparing performance of: Array.from vs manual vs spread

Created: 7 years ago by: Guest

Jump to the latest result

Array.from

manual

spread

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):