Benchmark: flatMap vs reduces

Script Preparation code:

var arr = Array(10_000).fill(0)

Tests:

reduce with concat
arr.reduce((acc, x) => [...acc, x, x], [])
flatMap
arr.flatMap(x => [x, x])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce with concat
flatMap

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 benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares the performance of two different approaches: `flatMap` and `reduce` (with `concat`) on an array of 10,000 elements.

**What are we testing?**

We're testing how quickly these two functions can process an array by:

1. Flattening it using `flatMap`
2. Reducing it using `reduce` with `concat`

**Options compared**

There are three options being compared:

1. **flatMap**: This function returns a new array with the results of applying the provided function to each element in the original array.
2. **reduce**: This function reduces an array to a single value, by iterating over it and applying the provided function to each element.

**Pros and Cons**

Here are some pros and cons of each approach:

1. **flatMap**
	* Pros:
		+ Can be more efficient than `reduce` with `concat`, especially for large arrays.
		+ Can handle nested arrays out-of-the-box.
	* Cons:
		+ May not work as expected if the provided function returns an array (instead of a single value).
2. **reduce** with `concat`
	* Pros:
		+ More predictable and easier to understand, especially for developers familiar with functional programming.
		+ Can handle arrays of any size.
	* Cons:
		+ May be slower than `flatMap` due to the extra overhead of concatenating arrays.

**Library usage**

There is no explicit library being used in this benchmark. However, it's worth noting that `reduce` and `concat` are built-in functions in JavaScript.

**Special JS feature or syntax**

This benchmark does not use any special features or syntax beyond standard JavaScript. It only uses the built-in `Array.prototype.flatMap` and `Array.prototype.reduce` methods.

**Other alternatives**

If you wanted to implement these functions from scratch, here's how you might do it:

1. **flatMap**: You could iterate over each element in the array and create a new array with the results of applying the provided function.
```javascript
arr.flatMap(x => [x, x])
```
becomes

```javascript
let result = [];
for (let i = 0; i < arr.length; i++) {
  result.push(arr[i], arr[i]);
}
return result;
```

2. **reduce**: You could iterate over each element in the array and keep accumulating a value by applying the provided function to each element.

```javascript
arr.reduce((acc, x) => [...acc, x, x], [])
```
becomes

```javascript
let acc = [];
for (let i = 0; i < arr.length; i++) {
  acc.push(arr[i]);
  acc.push(arr[i]);
}
return acc;
```

Keep in mind that these implementations would likely be slower than the built-in functions.

**Benchmark interpretation**

The benchmark results show that `flatMap` is significantly faster than `reduce` with `concat` on this particular array. This suggests that `flatMap` may be a better choice when you need to process arrays of any size and don't mind returning an array as output. However, without more context or knowledge of the specific use case, it's difficult to say which approach is "better" in general.

Related benchmarks:

flatMap vs reduces (version: 0)

Comparing performance of: reduce with concat vs flatMap

Created: 4 years ago by: Guest

Jump to the latest result

reduce with concat

flatMap

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):