Benchmark: Reduce and Spread vs. Foreach test

Script Preparation code:

var objectsArray = Array(1000).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}), {});
ForEach and Mutate (for .. in loop)
var combined = {} objectsArray.forEach(obj => { for (key in obj) { combined[key] = obj[key]; } });
Foreach and Mutate (Object.assign)
var combined = {} objectsArray.forEach(obj => Object.assign(combined, obj));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

**Overview**

The provided JSON represents a benchmark test case for measuring the performance of three different approaches to merge and process an array of objects in JavaScript:

1. `Reduce` with object spread
2. `Foreach` with a traditional `for...in` loop
3. `Foreach` using `Object.assign`

**Tested Approaches**

Here's a brief explanation of each approach:

### 1. Reduce with Object Spread

This approach uses the `reduce()` method to iterate over the array and merge the objects into a single object. The object spread operator (`{...memo, ...obj}`) is used to merge the properties of two objects.

**Pros:**

* Efficient use of memory
* Fast iteration over the array
* Can be more concise than other approaches

**Cons:**

* Limited control over the merging process
* May not work as expected for non-numeric keys or nested objects

### 2. Foreach with Traditional `for...in` Loop

This approach uses a traditional `for...in` loop to iterate over the array and merge the objects into a single object.

**Pros:**

* Easy to understand and implement
* Can be used with any type of key (numeric or string)
* Allows for more control over the merging process

**Cons:**

* Less efficient than other approaches due to the use of a loop
* May lead to slower performance due to the overhead of the loop

### 3. Foreach using `Object.assign()`

This approach uses the `Object.assign()` method to merge the objects into a single object.

**Pros:**

* Fast and efficient
* Easy to understand and implement
* Can be used with any type of key (numeric or string)

**Cons:**

* Less memory-efficient than other approaches due to the creation of new objects

**Library Used**

None, as these approaches are native JavaScript methods.

**Special JS Feature/Syntax**

No special features or syntax are used in this benchmark. However, note that some browsers may have different behavior for certain properties (e.g., `const` declarations) due to their engines' optimizations.

**Other Alternatives**

Some alternative approaches to merging arrays of objects include:

* Using a library like Lodash (`_.merge()`, `_objectAssign()`)
* Utilizing the `Array.prototype.reduce()` method with a custom merger function
* Leveraging modern JavaScript features like `map()` and `reduce()` together

In general, the choice of approach depends on the specific use case, performance requirements, and personal preference.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36

Browser/OS: Chrome 104 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Reduce and Spread	54851.9 Ops/sec
ForEach and Mutate (for .. in loop)	154017.7 Ops/sec
Foreach and Mutate (Object.assign)	11601.8 Ops/sec

Related benchmarks:

Reduce and Spread vs. Foreach test (version: 0)

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

Created: 2 years ago by: Guest

Jump to the latest result

Reduce and Spread

ForEach and Mutate (for .. in loop)

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 one month ago):