Benchmark: Mutate array vs memory efficient map

Mutate array vs memory efficient map (version: 0)

In memory constrained devices the use of .map() is not always possible. In such places, this should determine whether a mutation is better than creating a new array from scratch while emptying the original array, thus, keeping somewhat the same memory usage.

Comparing performance of: Mutate array vs Memory efficient map

Created: one year ago by: Guest

Jump to the latest result

Script Preparation code:

var test = [];

for (let i = 0; i < 100000; i++) {
  test.push(i);
}

Tests:

Mutate array
for (let i = 0; i < test.length; i++) { test[i] = i * 2; }
Memory efficient map
const copyTest = []; for (let i = 0; i < test.length; i++) { const currentItem = test.shift(); copyTest.push(currentItem * 2); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Mutate array
Memory efficient map

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The provided benchmark definition represents a comparison between two approaches:

1.  **Mutate array**: This approach involves modifying an existing array by assigning a new value to each element. The script preparation code pushes 100,000 elements onto the `test` array.
2.  **Memory efficient map**: This approach uses the `map()` method to create a new array with modified values without altering the original array. Instead, it creates a copy of the original array using `shift()`, modifies the copied array, and then pushes the modified elements back into the `copyTest` array.

**Options Compared**

The two approaches are being compared in terms of their performance:

*   **Memory usage**: The goal is to determine which approach minimizes memory usage while still achieving the desired mutation.
*   **Execution time**: The benchmark measures how many executions per second each approach can complete within a given timeframe.

**Pros and Cons**

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

1.  **Mutate array**
    *   Pros:
        *   Simplistic implementation
        *   May be more familiar to developers who are used to working with arrays
    *   Cons:
        *   Can lead to excessive memory usage due to the creation of a new, large array
        *   May not perform well in memory-constrained environments
2.  **Memory efficient map**
    *   Pros:
        *   Can help minimize memory usage by avoiding the creation of unnecessary arrays
        *   Uses built-in methods for array manipulation, making it potentially more efficient
    *   Cons:
        *   Requires a deeper understanding of JavaScript's `map()` method and its behavior
        *   May be less intuitive for developers who are not familiar with this approach

**Library or Special JS Feature**

The benchmark uses the `map()` method, which is a built-in JavaScript function that creates a new array by performing an operation on each element of an existing array. The `shift()` method is also used to remove elements from the original array and return them as an array.

There are no special JavaScript features or syntax mentioned in this benchmark definition.

**Alternatives**

If you're interested in exploring alternative approaches, here are a few options:

*   **Using a custom mutation function**: Instead of using `map()` or modifying arrays directly, you could create a custom function that mutates the original array by applying the desired transformation.
*   **Using a library like Lodash**: If you need to perform more complex data transformations, consider using a library like Lodash, which provides a wide range of utility functions for working with arrays and other data structures.

For this specific benchmark, MeasureThat.net is providing a straightforward comparison between two approaches. You can use the insights gained from this benchmark to inform your own coding decisions when working with JavaScript arrays.

Latest run results:

Run details: (Test run date: 4 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Mutate array	85.0 Ops/sec
Memory efficient map	15264040.0 Ops/sec

Related benchmarks: