Benchmark: Reduce and Spread vs. Foreach and Mutate (fewer, but larger, objects)

Script Preparation code:

var objectsArray = Array(10).fill(() => {
  return Object.fromEntries(Array(100).fill(() => {
    const key = Math.random().toString(36).substring(2, 5);
    const value = Math.random().toString(36).substring(2, 5);
    return [key, value];
  }));
});

AخA
 
var objectsArray = Array(10).fill(() => {  return Object.fromEntries(Array(100).fill(() => {    const key = Math.random().toString(36).substring(2, 5);    const value = Math.random().toString(36).substring(2, 5);    return [key, value];  }));});

Tests:

Reduce and Spread
var combined = objectsArray.reduce((memo, obj) => ({...memo, ...obj}), {});
var combined = objectsArray.reduce((memo, obj) => ({...memo, ...obj}), {});
ForEach and Mutate (for .. in loop)
var combined = {} objectsArray.forEach(obj => { for (const key in obj) { combined[key] = obj[key]; } });
var combined = {}
objectsArray.forEach(obj => {
for (const key in obj) {
combined[key] = obj[key];
}
});
Mutate with Object.assign
var combined = Object.assign(...objectsArray)
var combined = Object.assign(...objectsArray)
Foreach and Mutate (Object.assign)
var combined = {} objectsArray.forEach(obj => Object.assign(combined, obj));
var combined = {}
objectsArray.forEach(obj => Object.assign(combined, obj));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Experimental features:

Memory measurements supported only in Chrome.
For precise memory measurements Chrome must be launched with --enable-precise-memory-info flag.
More information: Monitoring JavaScript Memory

Test case name	Result
Reduce and Spread
ForEach and Mutate (for .. in loop)
Mutate with Object.assign
Foreach and Mutate (Object.assign)

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/132.0.6834.78 Mobile/15E148 Safari/604.1

Browser/OS: Chrome Mobile iOS 132 on iOS 18.2.1

View result in a separate tab

Test name	Executions per second
Reduce and Spread	1175197.1 Ops/sec
ForEach and Mutate (for .. in loop)	1089860.5 Ops/sec
Mutate with Object.assign	1723426.0 Ops/sec
Foreach and Mutate (Object.assign)	1511515.1 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 4 months ago):

Let's dive into the world of JavaScript microbenchmarks!

Benchmark Overview

The provided benchmark compares four different approaches to merge multiple objects in JavaScript:

Reduce with spread operator (...)
ForEach loop with mutation using key-value pairs
Mutate using Object.assign()
ForEach loop with object assignment using Object.assign() method

Options Compared

The benchmark tests the performance of each approach on a large dataset of 10 objects, each containing 100 randomly generated key-value pairs.

Reduce: uses the reduce() method to merge objects by spreading their properties into a single object.
ForEach loop with mutation: uses a for...in loop to iterate over the object's properties and assign values to a new object using bracket notation (combined[key] = obj[key];).
Mutate with Object.assign(): uses the Object.assign() method to merge objects by copying their properties into a single object.
ForEach loop with Object.assign(): similar to the previous approach, but uses the Object.assign() method to assign values from one object to another.

Pros and Cons

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

Reduce: Pros: concise, efficient; Cons: may not be as readable for complex datasets.
ForEach loop with mutation: Pros: flexible, can handle nested objects; Cons: slower due to iteration and bracket notation.
Mutate with Object.assign(): Pros: simple, reliable; Cons: assumes a specific object structure (e.g., all properties are enumerable).
ForEach loop with Object.assign(): Pros: readable, avoids mutation issues; Cons: may be slower due to repeated method calls.

Library Usage

The benchmark uses Object.fromEntries() and Array.prototype.fill() which are part of the ECMAScript standard (ES6). No external libraries are required.

Special JS Features/Syntax

None mentioned in the provided code snippet. However, it's worth noting that modern JavaScript engines often use various optimizations, such as just-in-time compilation, caching, or parallel execution, which can affect benchmark results.

Other Alternatives

If you're interested in exploring other approaches, consider the following alternatives:

Array.prototype.reduce() with a callback function to merge objects.
Using a library like Lodash (which provides merge and assignInPlace functions) for more complex object merging.
Employing a library like Ramda (which offers mergeBy and mapValues functions) for functional programming approaches.

Please keep in mind that the best approach will depend on your specific use case, data structure, and performance requirements.

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

**Benchmark Overview**

The provided benchmark compares four different approaches to merge multiple objects in JavaScript:

1. `Reduce` with spread operator (`...`)
2. `ForEach` loop with mutation using `key`-`value` pairs
3. `Mutate` using `Object.assign()`
4. `ForEach` loop with object assignment using `Object.assign()` method

**Options Compared**

The benchmark tests the performance of each approach on a large dataset of 10 objects, each containing 100 randomly generated key-value pairs.

* **Reduce**: uses the `reduce()` method to merge objects by spreading their properties into a single object.
* **ForEach loop with mutation**: uses a `for...in` loop to iterate over the object's properties and assign values to a new object using bracket notation (`combined[key] = obj[key];`).
* **Mutate with Object.assign()**: uses the `Object.assign()` method to merge objects by copying their properties into a single object.
* **ForEach loop with Object.assign()**: similar to the previous approach, but uses the `Object.assign()` method to assign values from one object to another.

**Pros and Cons**

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

1. **Reduce**: Pros: concise, efficient; Cons: may not be as readable for complex datasets.
2. **ForEach loop with mutation**: Pros: flexible, can handle nested objects; Cons: slower due to iteration and bracket notation.
3. **Mutate with Object.assign()**: Pros: simple, reliable; Cons: assumes a specific object structure (e.g., all properties are enumerable).
4. **ForEach loop with Object.assign()**: Pros: readable, avoids mutation issues; Cons: may be slower due to repeated method calls.

**Library Usage**

The benchmark uses `Object.fromEntries()` and `Array.prototype.fill()` which are part of the ECMAScript standard (ES6). No external libraries are required.

**Special JS Features/Syntax**

**Other Alternatives**

If you're interested in exploring other approaches, consider the following alternatives:

1. `Array.prototype.reduce()` with a callback function to merge objects.
2. Using a library like Lodash (which provides `merge` and `assignInPlace` functions) for more complex object merging.
3. Employing a library like Ramda (which offers `mergeBy` and `mapValues` functions) for functional programming approaches.

Please keep in mind that the best approach will depend on your specific use case, data structure, and performance requirements.

Related benchmarks:

Reduce and Spread vs. Foreach and Mutate (fewer, but larger, objects) (version: 0)

Comparing performance of: Reduce and Spread vs ForEach and Mutate (for .. in loop) vs Mutate with Object.assign vs Foreach and Mutate (Object.assign)

Created: 4 years ago by: Guest

Jump to the latest result

Reduce and Spread

ForEach and Mutate (for .. in loop)

Mutate with Object.assign

Foreach and Mutate (Object.assign)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 4 months ago):