Benchmark: Reduce + spread vs forEach + mutate

Tests:

Reduce + spread
const fields = ['aye','bee','cee'] const fromObject = { aye: 1, bee: 2, cee: 3, dee: 4 } const attributes = fields.reduce((attrs, field) => ({ ...attrs, [field]: fromObject[field] }))
forEach + mutate
const fields = ['aye','bee','cee'] const fromObject = { aye: 1, bee: 2, cee: 3, dee: 4 } const attributes = {} fields.forEach(field => { attributes[field] = fromObject[field] })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Reduce + spread
forEach + mutate

Fastest: N/A

Slowest: N/A

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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 the provided benchmark and explain what's being tested, compared, and analyzed.

**What is being tested?**

The benchmark is comparing two approaches to create an object with dynamic attributes:

1. **Reduce + Spread**: Using `Array.prototype.reduce()` to iterate over an array of strings (`fields`) and creating a new object (`attributes`) by spreading the properties from another object (`fromObject`) onto it.
2. **forEach + Mutate**: Iterating over an array of strings (`fields`) using `Array.prototype.forEach()` and adding each string as a key to the `attributes` object, assigning a value from `fromObject`.

**Options being compared**

The benchmark is comparing these two approaches:

*   Reduce + Spread: A concise way to create objects with dynamic attributes, utilizing the `reduce()` method.
*   forEach + Mutate: A more explicit approach using `forEach()` and mutating the `attributes` object.

**Pros and Cons of each approach:**

1.  **Reduce + Spread**:
    *   Pros:
        *   Concise and readable
        *   Efficient, as it avoids creating a new object for each iteration
    *   Cons:
        *   Less explicit about what's happening (might be harder to understand for beginners)
2.  **forEach + Mutate**:
    *   Pros:
        *   More explicit and understandable, especially for those familiar with `forEach()`
        *   Can be beneficial when debugging or logging
    *   Cons:
        *   Less efficient due to the need for multiple object assignments

**Library and purpose**

In this benchmark, there are no external libraries being used.

**Special JS feature/syntax**

There's a minor detail: in some cases, JavaScript will automatically create an empty object if you try to access a property on `undefined`. This is known as the "optional chaining operator" (`?.`), but it's not explicitly used in this benchmark. If you wanted to use it for additional error handling or optimization, you might do something like:

```javascript
const attributes = fields.reduce((attrs, field) => ({ ...attrs, [field]: fromObject[field] } || {}), {});
```

However, since the `reduce()` method directly returns an object (or undefined if reduced to falsey), this optimization isn't necessary here.

**Other alternatives**

There are a few alternative approaches you might consider:

*   Using a more functional programming style with `Array.prototype.reduceRight()` or `Array.prototype.map()`, which could provide different trade-offs in terms of efficiency and readability.
*   Utilizing modern JavaScript features like template literals, which can make code more readable at the expense of potentially lower performance due to additional overhead.

Keep in mind that, in this specific benchmark, both approaches have relatively similar performance characteristics. However, depending on your use case or requirements, you might prefer one over the other based on readability, maintainability, and any additional features you want to support.

**Considerations**

Some considerations when approaching this benchmark:

*   Pay attention to your specific use case: Are there unique edge cases that would benefit from a particular approach? Do you need to prioritize performance or readability above all else?
*   Be mindful of potential pitfalls: Avoid relying on implicit behavior like optional chaining (`?.`) unless absolutely necessary.
*   Keep things concise and readable: Aim for an optimal balance between efficiency, maintainability, and understanding.

Feel free to ask me any more questions regarding your specific benchmarking needs!

Related benchmarks:

Reduce + spread vs forEach + mutate (version: 0)

Comparing performance of: Reduce + spread vs forEach + mutate

Created: 2 years ago by: Guest

Jump to the latest result

Reduce + spread

forEach + mutate

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):