Benchmark: Reduce and Spread vs. Foreach and Mutate

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]; } });
Mutate with Object.assign
var combined = Object.assign(...objectsArray)
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)
Mutate with Object.assign
Foreach and Mutate (Object.assign)

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; rv:130.0) Gecko/20100101 Firefox/130.0

Browser/OS: Firefox 130 on Linux

View result in a separate tab

Test name	Executions per second
Reduce and Spread	5187.0 Ops/sec
ForEach and Mutate (for .. in loop)	1095.9 Ops/sec
Mutate with Object.assign	11274.5 Ops/sec
Foreach and Mutate (Object.assign)	8905.8 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, "Reduce and Spread vs. Foreach and Mutate", compares the performance of four different approaches to merge an array of objects into a single object.

**Approaches Compared**

1. **Reduce and Spread**: This approach uses the `reduce()` method with the spread operator (`...`) to merge the objects.
2. **ForEach and Mutate (for .. in loop)**: This approach uses a traditional `for` loop to iterate over the array of objects and assign each property to the resulting object using the dot notation (`obj[key] = combined[key]`).
3. **Mutate with Object.assign**: This approach uses the `Object.assign()` method to merge the objects.
4. **Foreach and Mutate (Object.assign)**: Similar to the previous one, but uses `Object.assign()` inside a `forEach` loop.

**Pros and Cons of Each Approach**

1. **Reduce and Spread**:
	* Pros: Efficient, concise, and modern syntax.
	* Cons: May not be supported in older browsers or versions of JavaScript that don't have this method (e.g., Internet Explorer 11).
2. **ForEach and Mutate (for .. in loop)**:
	* Pros: Widely supported across different browsers and versions of JavaScript.
	* Cons: Can be verbose, error-prone, and less readable than other approaches.
3. **Mutate with Object.assign**:
	* Pros: Familiar syntax for developers who have worked with `Object.assign()` before.
	* Cons: May not be the most efficient way to merge objects, as it creates a new object each time.
4. **Foreach and Mutate (Object.assign)**:
	* Pros: Similar to the previous one, but avoids the potential issue of creating too many intermediate objects.
	* Cons: Still may not be the most efficient approach.

**Library Used**

In this benchmark, `Array.prototype.reduce()` is used as a built-in JavaScript method. No external libraries are required.

**Special JS Feature or Syntax**

The `Object.assign()` method and the spread operator (`...`) are features introduced in ECMAScript 2015 (ES6). While not strictly necessary for older browsers, they can provide a more concise and modern way of performing certain tasks.

**Other Alternatives**

If you want to explore other approaches, you might consider:

* Using `concat()` instead of spread operator (`...`).
* Using `slice()` to create a shallow copy of the array before merging.
* Using a third-party library like Lodash or Underscore.js for utility functions like `merge()` or `reduce()`.
* Using a different data structure, such as an object with nested properties, instead of an array of objects.

Keep in mind that each approach has its trade-offs and may be better suited for specific use cases.

Related benchmarks:

Reduce and Spread vs. Foreach and Mutate (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: 5 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>

Fastest: N/A

Slowest: N/A

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