Benchmark: reduce with and without spread syntax

Script Preparation code:

var data = { ...Array.from(Array(10000).keys()) };

Tests:

reduce
Object.entries(data).reduce((acc, [k, v]) => { acc[k] = v.toString(); return acc; }, {});
map + fromEntries
Object.entries(data).reduce((acc, [k, v]) => ({...acc, [k]:v.toString()}),{})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce
map + fromEntries

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark is testing two different approaches for reducing an object in JavaScript:

1. **reduce**: This approach uses the `reduce()` method directly on the `Object.entries()` returned by `Array.from(Array(10000).keys())`. The callback function takes three arguments: the accumulator (`acc`), the key-value pair from `Object.entries()`, and returns the updated accumulator.
2. **map + fromEntries**: This approach uses `map()` to create a new array of strings, where each string is created by calling `toString()` on the value in the object, and then uses `fromEntries()` to convert this array back into an object.

**Options Compared**

The two approaches are being compared in terms of their execution speed. The benchmark is trying to determine which approach is faster for reducing a large object.

**Pros and Cons**

* **reduce**:
	+ Pros: This approach is concise and uses built-in JavaScript methods, making it easy to read and understand.
	+ Cons: It may be less efficient due to the overhead of creating an array and then converting it back into an object using `fromEntries()`.
* **map + fromEntries**:
	+ Pros: This approach avoids the overhead of creating a new array and converting it back into an object, making it potentially faster.
	+ Cons: It may be less concise and more verbose than the `reduce()` approach.

**Library**

The `fromEntries()` method is used in the second test case. The `fromEntries()` function is part of the ECMAScript 2019 standard and is included in modern browsers, including Chrome 88. Its purpose is to convert an iterable (such as an array) into an object.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark beyond what's already mentioned (`fromEntries()`).

**Other Alternatives**

If you want to test alternative approaches for reducing an object, here are a few options:

* Using `forEach()` instead of `reduce()`: This would involve using the callback function passed to `forEach()` to update the accumulator.
* Using a loop with indexing: Instead of using `Object.entries()`, you could use a traditional loop with indexing to iterate over the object's properties and values.

Here's an example of how you might write a benchmark for reducing an object using a loop:
```javascript
var data = { ...Array.from(Array(10000).keys()) };
var startTime = performance.now();
for (var k in data) {
  acc[k] = v.toString();
}
console.log(performance.now() - startTime);
```
Keep in mind that this approach would be slower than the `reduce()` method, as it involves a manual loop instead of relying on built-in JavaScript methods.

Related benchmarks:

reduce with and without spread syntax (version: 0)

Comparing performance of: reduce vs map + fromEntries

Created: 5 years ago by: Guest

Jump to the latest result

reduce

map + fromEntries

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):