Benchmark: Array Spread vs Fill vs New Array

Tests:

New Array
[...new Array(5)].map(Object);
Fill
new Array(5).fill(null).map(Object);
Map
[...Array(5)].map(Object);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
New Array
Fill
Map

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Browser/OS: Chrome 138 on Linux

View result in a separate tab

Test name	Executions per second
New Array	12266862.0 Ops/sec
Fill	7957847.0 Ops/sec
Map	9680335.0 Ops/sec

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 MeasureThat.net and explore what's being tested in this specific benchmark.

**Benchmark Overview**

The benchmark is designed to compare three approaches for creating an array in JavaScript:

1. Using the spread operator (`[...new Array(5)].map(Object);`)
2. Using the `fill()` method (`new Array(5).fill(null).map(Object);`)
3. Creating a new array using the traditional syntax (`new Array(5).map(Object);`)

**Options Compared**

The three options being compared are:

* **New Array**: Creates a new array using the `new Array()` constructor and then maps over it.
* **Fill**: Fills an existing array with null values and then maps over it.
* **Spread Operator**: Uses the spread operator (`[...new Array(5)]`) to create a new array, which is then mapped over.

**Pros and Cons of Each Approach**

Here's a brief summary of the pros and cons of each approach:

1. **New Array**:
	* Pros: More explicit, easier to understand for beginners.
	* Cons: Can be slower due to the overhead of creating an intermediate array.
2. **Fill**:
	* Pros: Faster than `new Array`, as it reuses an existing array.
	* Cons: May lead to unexpected behavior if not used carefully (e.g., filling a large array with null values).
3. **Spread Operator**:
	* Pros: Concise, modern syntax that's widely adopted in JavaScript.
	* Cons: Can be slower than `new Array` due to the overhead of creating an intermediate array.

**Library and Special JS Features**

There is no library used in this benchmark. Additionally, there are no special JavaScript features being tested (e.g., async/await, Promises).

**Other Considerations**

When comparing these approaches, it's essential to consider the following:

* **Memory allocation**: Creating a new array can lead to additional memory allocation, which may impact performance.
* **Overhead of intermediate arrays**: The spread operator creates an intermediate array, which can add overhead compared to the traditional `new Array()` approach.
* **Cache locality**: Filling an existing array with null values may improve cache locality, making subsequent operations faster.

**Alternatives**

If you're looking for alternatives or variations on this benchmark, consider the following:

* Test using a larger array size (e.g., 10, 20, 50) to observe scaling effects.
* Compare the performance of these approaches with other methods, such as using `Array.from()` or `Array.prototype.slice()`.
* Investigate the impact of using different data types (e.g., numbers, strings, objects) on the benchmark results.

By exploring these alternatives and considerations, you can gain a deeper understanding of the trade-offs involved in each approach and make informed decisions about which method to use in your own code.

Related benchmarks:

Array Spread vs Fill vs New Array (version: 0)

Comparing performance of: New Array vs Fill vs Map

Created: one year ago by: Guest

Jump to the latest result

New Array

Fill

Map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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