Benchmark: reassigning an object

Script Preparation code:

var array = [{
        id: 1,
        name: 'Item 1'
    },
    {
        id: 2,
        name: 'Item 2'
    },
    {
        id: 3,
        name: 'Item 3'
    }
];

var newObject = {
    id: 2,
    name: 'Updated Item 2'
};

Tests:

map
var index = array.findIndex(item => item.id === newObject.id); if (index !== -1) { array[index] = newObject; }
index
var index = array.findIndex(item => item.id === newObject.id); // Only proceed if the item is found var updatedArray; if (index !== -1) { updatedArray = [ ...array.slice(0, index), // Elements before the updated item newObject, // The updated item ...array.slice(index + 1) // Elements after the updated item ]; } else { // If the item isn't found, the array remains unchanged updatedArray = array; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map
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/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

map

7.0M/s

index

4.6M/s

View exact numbers

Test name	Executions per second
✓ map	7,028,268 Ops/sec
index	4,574,258 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmarking test case, which measures the performance of two approaches: using `map()` and using an index to replace a specific element in an array.

**Options Compared**

Two options are compared:

1. **Using `map()`**: This approach creates a new array by mapping each element in the original array to a new value. In this case, it replaces the existing elements with a new object.
2. **Using an index to replace an element**: This approach uses the `findIndex()` method to find the index of the element that needs to be replaced and then creates a new array by concatenating the elements before, after, and the updated element.

**Pros and Cons**

### Using `map()`

Pros:

* Concise and expressive code
* Easy to read and maintain

Cons:

* Creates a new array, which can be memory-intensive for large datasets
* May have performance overhead due to array creation and iteration

### Using an index to replace an element

Pros:

* Avoids creating a new array, reducing memory usage
* Can be more efficient than `map()` for large datasets

Cons:

* Code is more verbose and complex
* Requires careful handling of edge cases (e.g., null or undefined elements)

**Library**

In the provided code, the `findIndex()` method is used to find the index of the element that needs to be replaced. This method is part of the Array prototype in JavaScript and is not a separate library.

**Special JS Feature/Syntax**

No special JavaScript features or syntax are used in this benchmark.

**Alternative Approaches**

Other approaches to replace an element in an array include:

1. **Using `splice()`**: Replaces elements by removing and inserting at the specified index.
2. **Using a loop**: Iterates over the array, finding and replacing the desired element using indexing or iteration.
3. **Using a library like Lodash**: Provides a `set` function that replaces elements in an array.

Each approach has its own trade-offs in terms of performance, memory usage, and code complexity. The choice of approach depends on the specific requirements and constraints of the use case.

**Benchmark Preparation Code Explanation**

The script preparation code creates an initial array with three elements and a new object `newObject`. This setup is used to test the two approaches: using `map()` and using an index to replace an element.

The individual test cases are defined in the JSON array, each specifying the benchmark definition, test name, and execution settings.

reassigning an object (version: 0) Benchmark.js

Comparing performance of: `map vs index`

Created: 2 years ago by: Guest

Go to the latest result

map

index

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

reassigning an object (version: 0) Benchmark.js

Comparing performance of: map vs index

Created: 2 years ago by: Guest

Go to the latest result

map

index

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `map vs index`