Benchmark: Transform dict values: for vs fromEntries 2

Script Preparation code:

function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

function generateRandomArray(length) {
  return Array.from({ length }, () => getRandomInt(1, 1000)); // Random values, but values themselves don't matter
}

function generateRandomDict(numEntries, maxArrayLength) {
  const dict = {};
  
  for (let i = 0; i < numEntries; i++) {
    const key = `key${i + 1}`;
    const arrayLength = getRandomInt(1, maxArrayLength);
    dict[key] = generateRandomArray(arrayLength);
  }
  
  return dict;
}

// Configuration
const numEntries = getRandomInt(1, 99); // Less than 100 entries
const maxArrayLength = 99; // Each array has less than 100 elements

// Generate the dictionary
var randomDict = generateRandomDict(numEntries, maxArrayLength);

console.log(randomDict);

Tests:

For each
const transformedForEach = {}; for (const key of Object.keys(randomDict)) { const arr = randomDict[key]; transformedForEach[key] = arr.map((item) => item * 2); }
fromEntries()
const transformedFromEntries = Object.fromEntries( Object.entries(randomDict).map(([key, arr]) => [ key, arr.map((item) => item * 2), ]), );

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For each
fromEntries()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36

Browser/OS: Chrome 125 on Linux

View result in a separate tab

Test name	Executions per second
For each	305014.3 Ops/sec
fromEntries()	245029.9 Ops/sec

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.

**What is being tested?**

The test cases are comparing the performance of two approaches to transform dictionary values:

1. **`for...of` loop**: The first approach uses a `for...of` loop to iterate over the dictionary keys and then maps each value in the corresponding array.
2. **`Object.entries()` and `Array.prototype.map()`**: The second approach uses `Object.entries()` to get an array of key-value pairs, maps over this array to transform each pair into a new object with transformed values, and then converts the resulting array back into an object using `Object.fromEntries()`.

**Options compared**

The two approaches are being compared for their performance. In terms of implementation details, these options differ:

1. **`for...of` loop**: This approach uses a traditional `for...of` loop to iterate over the dictionary keys.
2. **`Object.entries()` and `Array.prototype.map()`**: This approach uses the built-in `Object.entries()` method to get an array of key-value pairs, which is then mapped over using `Array.prototype.map()`. Finally, the resulting array is converted back into an object using `Object.fromEntries()`.

**Pros and cons**

Here's a brief overview of the pros and cons of each approach:

1. **`for...of` loop**:
	* Pros: Simple, intuitive implementation.
	* Cons: May be slower due to the overhead of dynamic typing and iteration.
2. **`Object.entries()` and `Array.prototype.map()`**:
	* Pros: Often faster than traditional loops, as it leverages built-in methods that are optimized for performance.
	* Cons: Requires understanding of new array methods, which may add complexity.

**Special considerations**

The test case uses a random dictionary with varying key lengths and values. The `for...of` loop approach is less prone to issues related to variable length arrays, as the loop iterates over keys regardless of their length. In contrast, the `Object.entries()` and `Array.prototype.map()` approach may require more careful handling of edge cases related to array lengths.

**Library or framework usage**

There are no external libraries or frameworks used in this test case. Both approaches rely on built-in JavaScript methods and syntax.

**Special JS feature or syntax**

The test case does not use any special JavaScript features or syntax that might be specific to certain browsers or implementations.

**Alternative approaches**

Other possible approaches for transforming dictionary values could include:

1. **Using `forEach()`**: Similar to the `for...of` loop, but with a built-in method that iterates over arrays.
2. **Using `reduce()`**: Another array method that can be used to transform values in an array-like structure.
3. **Using `map()` directly on the dictionary**: Applying `Array.prototype.map()` directly to the dictionary values without iterating over keys could also be considered.

However, it's worth noting that using these alternatives might not provide a straightforward comparison with the current approaches, as they may involve different iteration patterns or transformations.

I hope this explanation helps!

Related benchmarks:

Transform dict values: for vs fromEntries 2 (version: 1)

Comparing performance of: For each vs fromEntries()

Created: one year ago by: Registered User

Jump to the latest result

For each

fromEntries()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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