Benchmark: create new Map vs create new Array

Tests:

new Array
let arr = [1,2,3,5,6,7,8,9,10,11,12,13] const filteredArr = arr.filter(item => item !== 1) const result = arr.find(item => item === 13) arr = filteredArr
new Map
const map = new Map([['1', '1'], ['2', '2'], ['3', '3'], ['4', '4'], ['5', '5'], ['6', '6'], ['7', '7'] ,['8', '8'] ,['9', '9']]) map.delete('2') const result = map.get('1') const updatedMap = new Map(map)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
new Array
new Map

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation of what's being tested on MeasureThat.net.

The provided JSON represents two individual test cases for JavaScript microbenchmarks:

**Test Case 1: Creating a new Array vs Filtering an existing Array**

This test case is designed to measure the performance difference between creating a new array and filtering an existing array. The benchmark script creates an initial array `arr` with 12 elements, then uses the `filter()` method to remove one element (`item === 1`). The resulting filtered array is assigned back to the original `arr`. Finally, the test finds the first occurrence of `item === 13` using the `find()` method and assigns it to a variable.

The pros of creating a new array for this scenario are:

* It's often easier to understand and maintain code that creates a new array instead of modifying an existing one.
* Creating a new array can help avoid side effects in the original array, making the code more predictable.

However, there are cons:

* Creating a new array requires extra memory allocation and copying of elements, which can be costly operations.
* If the filtered array is not used immediately, the assignment back to `arr` may not be necessary.

**Test Case 2: Creating a new Map vs Removing an existing key from a Map**

This test case measures the performance difference between creating a new map and removing an existing key from a map. The benchmark script creates a map with 9 entries using the `Map()` constructor, then removes one entry (`'2'`) using the `delete()` method. Finally, it retrieves the value associated with the removed key using the `get()` method.

Pros of creating a new Map for this scenario:

* Creating a new map allows you to start fresh and avoid potential side effects from modifying an existing map.
* Mappings in JavaScript are more efficient than arrays when it comes to inserting or removing elements dynamically.

However, there are cons:

* Creating a new map requires extra memory allocation and object creation, which can be costly operations.
* If the removed key is used later in the code, creating a new map may result in duplicate data.

**Comparison of Approaches**

The two approaches have different implications for performance, readability, and maintainability. Here's a summary:

| Approach | Pros | Cons |
| --- | --- | --- |
| Creating a new Array | Easier to understand, avoids side effects | Extra memory allocation and copying |
| Filtering an existing Array | Faster execution (no extra memory allocation) | More complex code |

| Approach | Pros | Cons |
| --- | --- | --- |
| Creating a new Map | Starts fresh, efficient for insertions/removals | Extra memory allocation and object creation |
| Removing from an existing Map | Efficient for key removals | Requires creating a new map if key is used later |

**Library: Lodash (not explicitly mentioned in the JSON)**

Although not directly related to the provided benchmark, it's worth mentioning that Lodash is often used in JavaScript development for utility functions like `filter()`. The use of this library can impact performance and readability, depending on the specific implementation.

**Special JS Feature: No special features are mentioned**

There are no special JavaScript features or syntax explicitly used in these benchmarks. However, it's worth noting that modern JavaScript features like async/await, Promises, and modernized `this` contexts (e.g., with `let this`, `const this`) might be used in more complex benchmark scripts.

**Alternatives**

If you need to measure performance for different data structures or operations, consider the following alternatives:

* Array-based benchmarks: Measure the performance of array-specific operations like `map()`, `filter()`, and `reduce()`.
* Object-based benchmarks: Measure the performance of object-specific operations like property access, key-value pairs, and object manipulation.
* DOM-related benchmarks: Measure the performance of DOM-related operations like node creation, event listeners, and rendering.

Keep in mind that these alternatives will likely have different performance characteristics and might require additional considerations for accurate benchmarking.

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
new Array	42055492.0 Ops/sec
new Map	1680701.2 Ops/sec

Related benchmarks:

create new Map vs create new Array (version: 0)

Comparing performance of: new Array vs new Map

Created: 8 months ago by: Registered User

Jump to the latest result

new Array

new Map

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):