Benchmark: Reduce vs Iterate

Script Preparation code:

var obj = {};
for (let index = 0; index < 10000; index++) {
  obj[index] = 'hello';
}

Tests:

Spread
const newObj = Object.keys(obj).reduce((rv, key) => ({ ...rv, [key]: obj[key].toUpperCase() }), {})
Iterate
const newObj = {}; for (const key of Object.keys(obj)) { const value = obj[key]; newObj[key] = value.toUpperCase(); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Iterate

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, compared, and their pros and cons.

**Benchmark Overview**

The benchmark compares two approaches to transform an object: using the `reduce()` method with the spread operator (`...`) versus iterating over the object keys. The benchmark creates a large object `obj` with 10,000 properties set to `'hello'`, then tests how quickly each approach can convert this object into a new object with uppercase values.

**Options Compared**

There are two options being compared:

1. **Reduce with Spread**: This method uses `Object.keys()` to get an array of keys from the original object, then iterates over that array using `forEach` (not explicitly mentioned in the benchmark definition but implied by the `reduce()` usage). The spread operator is used to create a new object with uppercase values.
2. **Iterate**: This approach uses `Object.keys()` to get an array of keys from the original object, then iterates over that array using `for...of` loop to access each key and value. The resulting object has uppercase values.

**Pros and Cons**

### Reduce with Spread

Pros:

* More concise code
* Avoids explicit iteration over keys

Cons:

* May have performance overhead due to creating an intermediate array of keys
* Might not be as efficient for very large objects due to the spread operator's complexity

### Iterate

Pros:

* Can be more straightforward and easy to understand
* Avoids potential performance issues with spread operator usage

Cons:

* More verbose code compared to the reduce approach
* Requires explicit iteration over keys, which might be slower than using `reduce()`

**Library Usage**

In this benchmark, no external libraries are used. The `Object.keys()` method is a built-in JavaScript function that returns an array of a given object's own enumerable property names.

**Special JS Feature/Syntax**

The spread operator (`...`) is being used in the reduce approach. This syntax was introduced in ECMAScript 2018 (ES10) and allows for creating new objects by "spreading" the values from an existing object into a new one.

The `for...of` loop is also used in the iterate approach, which is a newer iteration syntax introduced in ECMAScript 2017 (ES7).

**Other Alternatives**

If you were to reimplement this benchmark using different approaches, here are some alternatives:

* Using `forEach()` instead of `for...of`
* Using `Object.entries()` and `map()` instead of `Object.keys()`
* Using a custom iteration function or recursion
* Comparing with other ES6+ features like `Promise.all()`, async/await, or web workers

Keep in mind that each alternative would require significant changes to the benchmark code and might not offer significant performance benefits over the original approaches.

Related benchmarks:

Reduce vs Iterate (version: 0)

Comparing performance of: Spread vs Iterate

Created: 7 years ago by: Guest

Jump to the latest result

Spread

Iterate

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):