Benchmark: slice + mutation vs map

Script Preparation code:

var users = [
	{ 'user': 'joey',  'age': 32 },
 	{ 'user': 'ross',    'age': 41 },
  	{ 'user': 'chandler', 'age': 39 },
    	{ 'user': 'chandler', 'age': 39 },
      	{ 'user': 'chandler', 'age': 39 },
    	{ 'user': 'chandler', 'age': 39 },
    	{ 'user': 'chandler', 'age': 39 },
    	{ 'user': 'chandler', 'age': 39 },
    	{ 'user': 'chandler', 'age': 39 },
    	{ 'user': 'chandler', 'age': 39 },

]

Tests:

map
const res = users.map(user => user.user === 'ross' ? {...user, age: 50} : user)
splice + index
const res = [...users] res[1].age = 50

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map
splice + index

Fastest: N/A

Slowest: N/A

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/605.1.15 (KHTML, like Gecko) Version/15.4 Safari/605.1.15

Browser/OS: Safari 15 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
map	2569235.8 Ops/sec
splice + index	3991002.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is tested, compared options, pros and cons of each approach, and other considerations.

**Benchmark Definition**

The benchmark measures the performance of two approaches:

1. **map**: A function that creates a new array by applying a transformation function to each element in the original array.
2. **splice + index**: A function that modifies the original array by incrementing the age property of specific elements using `splice` and indexing.

**Options Compared**

Both approaches aim to transform or modify the `users` array, which contains six objects with duplicate values (e.g., multiple users named "Chandler").

**Approach 1: map**

The `map` approach uses the `Array.prototype.map()` method, which:

* Creates a new array with the same length as the original array.
* Applies the provided transformation function to each element in the original array.

In this case, the transformation function checks if the user's name is "Ross" and updates the age property if true. The resulting array contains the modified elements.

**Approach 2: splice + index**

The `splice + index` approach uses the `Array.prototype.splice()` method to increment the age property of specific elements:

* Creates a copy of the original array using the spread operator (`[...users]`).
* Modifies the copied array by incrementing the age property of elements at specific indices (starting from index 1).

This approach directly modifies the original array instead of creating a new one.

**Pros and Cons**

**map**

Pros:

* Creates a new array with the modified elements, which can be beneficial for certain use cases.
* Can be more efficient if the transformation function is expensive or complex.

Cons:

* Creates an additional array object, which can lead to increased memory usage.
* May be slower due to the overhead of creating a new array.

**splice + index**

Pros:

* Directly modifies the original array, reducing memory usage.
* Can be faster since it avoids creating a new array.

Cons:

* Modifies the original array in place, which might not be desirable for some use cases.
* Can lead to unnecessary updates if the transformation function is not expensive or complex.

**Other Considerations**

Both approaches have trade-offs between performance and memory usage. The choice between `map` and `splice + index` depends on the specific requirements of your use case:

* If you need to create a new array with modified elements, `map` might be a better choice.
* If you want to modify the original array in place or optimize for low memory usage, `splice + index` could be more suitable.

**Library and Special JS Features**

There are no libraries used in this benchmark. However, some JavaScript features like ES6 arrow functions (`=>`) and template literals (`\r\n\t{ ... }`) are used to define the transformation function.

No special JavaScript features or syntax are mentioned in the provided code.

**Alternatives**

If you need alternative approaches for similar problems, consider:

* **filter()**: Creates a new array with elements that pass a test provided as a function.
* **reduce()**: Applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

These methods can be used to transform or modify arrays in different ways, offering alternative approaches for specific use cases.

Related benchmarks:

slice + mutation vs map (version: 0)

Comparing performance of: map vs splice + index

Created: 2 years ago by: Guest

Jump to the latest result

map

splice + index

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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