Benchmark: reduce vs mutation

Tests:

reduce
const range = (from, to) => { const output = [] for(var i = from; i < to; i++){ output.push(i) } return output } const test = range(0, 100).reduce((acc, curr) => { acc[curr] = curr return acc }, {})
mutation
const range = (from, to) => { const output = [] for(var i = from; i < to; i++){ output.push(i) } return output } const test = {} range(0, 100).forEach((item) => { test[item] = item })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce
mutation

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.182 Safari/537.36

Browser/OS: Chrome 88 on Linux

View result in a separate tab

Test name	Executions per second
reduce	179641.1 Ops/sec
mutation	187502.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**Benchmark Definition and Test Cases**

The benchmark measures the performance difference between two approaches to populate an object: using the `Array.prototype.reduce()` method or using mutation (directly assigning values to the object).

**Options Compared**

Two options are compared:

1. **Reduce**: This approach uses the `Array.prototype.reduce()` method to iterate over the array and assign values to the object.
2. **Mutation**: This approach iterates over the array using a `for...of` loop and directly assigns values to the object.

**Pros and Cons**

**Reduce:**

Pros:

* More concise and expressive code
* Built-in support for iteration and accumulation in a single method

Cons:

* Potential performance overhead due to the creation of an accumulator object
* May not be as cache-friendly as mutation due to the way JavaScript optimizes array operations

**Mutation:**

Pros:

* Cache-friendly due to the direct assignment to the object's property
* Can potentially be faster than reduce for very large arrays

Cons:

* More verbose and less expressive code
* May require more manual memory management (e.g., handling null or undefined values)

**Library Used**

In this benchmark, no explicit library is used. The `Array.prototype.reduce()` method is a built-in JavaScript function.

**Special JS Feature or Syntax**

The `for...of` loop in the mutation test case uses a newer JavaScript feature introduced in ECMAScript 2015 (ES6). This loop allows iterating over an array without manually indexing into it, making the code more concise and expressive. However, this feature is not compatible with older browsers that do not support ES6.

**Other Considerations**

When considering performance-critical code, the choice between reduce and mutation ultimately depends on the specific use case and the trade-offs between conciseness, expressiveness, and performance. In general:

* Use `Array.prototype.reduce()` when:
	+ You need to accumulate values from an array into a single object.
	+ The code needs to be concise and expressive.
* Use direct assignment (mutation) when:
	+ You need to cache-friendly iteration over a large array.
	+ Performance is critical, and you can tolerate more verbose code.

**Alternatives**

If you're interested in exploring alternative approaches, consider the following:

* **Array.prototype.forEach()**: This method iterates over an array without creating an accumulator object. However, it's generally slower than `reduce()` due to the overhead of calling a separate function for each iteration.
* **Custom iteration loops**: You can write your own custom iteration loop using traditional indexing and assignment. This approach provides full control over performance but requires more manual memory management.

Keep in mind that these alternatives may not provide the same conciseness and expressiveness as `Array.prototype.reduce()`, which makes it a popular choice for many use cases.

Related benchmarks:

reduce vs mutation (version: 0)

Comparing performance of: reduce vs mutation

Created: 3 years ago by: Guest

Jump to the latest result

reduce

mutation

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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