Benchmark: reducer vs fromEntries

Script Preparation code:

vartest = test = Array(10000)
        .fill('')
        .map((_, i) => ({ key: 'key' + i, value: 'value' + i }));

Tests:

fromEntries
const result = Object.fromEntries(test.map(({ key, value }) => [key, value]));
reducer
const result2 = test.reduce((acc, { key, value }) => { acc[key] = value; return acc; }, {});
reducer with acc
const result3 = test.reduce((acc, { key, value }) => ({...acc, [key]: value}), {});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
fromEntries
reducer
reducer with acc

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Linux

View result in a separate tab

Test name	Executions per second
fromEntries	816.2 Ops/sec
reducer	2097.2 Ops/sec
reducer with acc	0.1 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided benchmark is designed to compare the performance of two approaches for creating an object from an array of key-value pairs: `Object.fromEntries` and the `reduce` method.

**Options Compared**

There are three test cases:

1. **From Entries**: Uses the `Object.fromEntries` method, which creates a new object by iterating over an iterable (in this case, an array) of key-value pairs.
2. **Reducer with Acc**: Uses the `reduce` method, which applies a callback function to each element in the array, accumulating a result object.

**Pros and Cons**

*   **Object.fromEntries**
    *   Pros:
        *   More concise and readable syntax
        *   Does not require iterating over the array twice (like the reducer approach)
    *   Cons:
        *   May have performance overhead due to the creation of an intermediate iterable object
*   **Reducer with Acc**
    *   Pros:
        *   Can be more efficient, as it avoids creating an intermediate iterable object
        *   Allows for more control over the accumulator object and key-value pairs iteration order
    *   Cons:
        *   More verbose syntax
        *   Requires iterating over the array twice (once to initialize the accumulator, once to update its values)

**Library**

In this benchmark, `Object.fromEntries` is used as a library function. It's a modern JavaScript method introduced in ECMAScript 2015 (ES6) that creates an object from an iterable of key-value pairs.

**Other Considerations**

When choosing between these two approaches, consider the following:

*   Performance: If you're dealing with large datasets or performance-critical code, the reducer approach might be more efficient.
*   Code Readability: The `Object.fromEntries` method is generally more concise and readable, making it a better choice for simple use cases.

**Alternative Approaches**

Other ways to create an object from an array of key-value pairs include:

*   **Array.prototype.reduce()**: Similar to the reducer approach, but without the accumulator object.
*   **Array.prototype.forEach()**: Iterates over the array and updates a target object. Not as efficient as `Object.fromEntries` or `reduce`, though.

Here's an example using `Array.prototype.reduce()`:
```javascript
const result = test.reduce((acc, { key, value }) => ({ ...acc, [key]: value }), {});
```
And here's an example using `Array.prototype.forEach()`, assuming a target object `obj`:
```javascript
test.forEach(({ key, value }) => obj[key] = value);
```

Note that the latter approach might not be suitable for all use cases, especially when dealing with large datasets or performance-critical code.

Related benchmarks:

reducer vs fromEntries (version: 0)

Comparing performance of: fromEntries vs reducer vs reducer with acc

Created: 2 years ago by: Guest

Jump to the latest result

fromEntries

reducer

reducer with acc

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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