Benchmark: reassigning an object with larger arrray

Script Preparation code:

var array = [
    {'id': 1, 'name': 'Item 1'},
    {'id': 2, 'name': 'Item 2'},
    {'id': 3, 'name': 'Item 3'},
    {'id': 4, 'name': 'Item 4'},
    {'id': 5, 'name': 'Item 5'},
    {'id': 6, 'name': 'Item 6'},
    {'id': 7, 'name': 'Item 7'},
    {'id': 8, 'name': 'Item 8'},
    {'id': 9, 'name': 'Item 9'},
    {'id': 10, 'name': 'Item 10'},
    {'id': 11, 'name': 'Item 11'},
    {'id': 12, 'name': 'Item 12'},
    {'id': 13, 'name': 'Item 13'},
    {'id': 14, 'name': 'Item 14'},
    {'id': 15, 'name': 'Item 15'},
    {'id': 16, 'name': 'Item 16'},
    {'id': 17, 'name': 'Item 17'},
    {'id': 1, 'name': 'Item 1'},
    {'id': 65, 'name': 'Item 2'},
    {'id': 3, 'name': 'Item 3'},
    {'id': 4, 'name': 'Item 4'},
    {'id': 5, 'name': 'Item 5'},
    {'id': 6, 'name': 'Item 6'},
    {'id': 7, 'name': 'Item 7'},
    {'id': 8, 'name': 'Item 8'},
    {'id': 9, 'name': 'Item 9'},
    {'id': 10, 'name': 'Item 10'},
    {'id': 11, 'name': 'Item 11'},
    {'id': 12, 'name': 'Item 12'},
    {'id': 13, 'name': 'Item 13'},
    {'id': 14, 'name': 'Item 14'},
    {'id': 15, 'name': 'Item 15'},
    {'id': 16, 'name': 'Item 16'},
    {'id': 17, 'name': 'Item 17'},
      {'id': 1, 'name': 'Item 1'},
    {'id': 28, 'name': 'Item 2'},
    {'id': 3, 'name': 'Item 3'},
    {'id': 4, 'name': 'Item 4'},
    {'id': 5, 'name': 'Item 5'},
    {'id': 6, 'name': 'Item 6'},
    {'id': 7, 'name': 'Item 7'},
    {'id': 8, 'name': 'Item 8'},
    {'id': 9, 'name': 'Item 9'},
    {'id': 10, 'name': 'Item 10'},
    {'id': 11, 'name': 'Item 11'},
    {'id': 12, 'name': 'Item 12'},
    {'id': 13, 'name': 'Item 13'},
    {'id': 14, 'name': 'Item 14'},
    {'id': 15, 'name': 'Item 15'},
    {'id': 16, 'name': 'Item 16'},
    {'id': 17, 'name': 'Item 17'},
    {'id': 1, 'name': 'Item 1'},
    {'id': 65, 'name': 'Item 2'},
    {'id': 3, 'name': 'Item 3'},
    {'id': 4, 'name': 'Item 4'},
    {'id': 5, 'name': 'Item 5'},
    {'id': 6, 'name': 'Item 6'},
    {'id': 7, 'name': 'Item 7'},
    {'id': 8, 'name': 'Item 8'},
    {'id': 9, 'name': 'Item 9'},
    {'id': 10, 'name': 'Item 10'},
    {'id': 11, 'name': 'Item 11'},
    {'id': 12, 'name': 'Item 12'},
    {'id': 13, 'name': 'Item 13'},
    {'id': 14, 'name': 'Item 14'},
    {'id': 15, 'name': 'Item 15'},
    {'id': 16, 'name': 'Item 16'},
    {'id': 17, 'name': 'Item 17'},
];

var newObject = { id: 2, name: 'Updated Item 2' };

Tests:

index
var index = array.findIndex(item => item.id === newObject.id); 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; }
map
var arr = array.map(item => { if (item.id === newObject.id) { return newObject; } return item; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
index
map

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

Test name	Executions per second
index	2794693.0 Ops/sec
map	462592.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the provided benchmark definition and test cases.

**Benchmark Definition**

The `reassigning an object with larger array` benchmark measures how fast JavaScript can reassign an object when its inner array is longer than the number of elements in the original array. The benchmark creates a large array, assigns it to a variable, and then updates it by assigning a new object that has one property (`id`) matching another property (`name`) from the original array.

**Options Compared**

The benchmark compares two approaches:

1. `index`: Uses `Array.prototype.findIndex` to find the index of the updated item in the original array. If found, it creates a new array with the updated item at that position. If not found, the original array remains unchanged.
2. `map`: Uses `Array.prototype.map` to create a new array with all elements transformed according to a provided function. In this case, if an element's `id` matches the updated object's `id`, it returns the updated object; otherwise, it returns the original element.

**Individual Test Cases**

The benchmark defines two test cases:

1. `index`: Tests the performance of finding and updating an item in the array using `Array.prototype.findIndex`.
2. `map`: Tests the performance of creating a new array with all elements transformed using `Array.prototype.map`.

**Benchmark Results**

The latest benchmark results show the execution frequency per second for each test case on Chrome 120, running on a Mac OS X 10.15.7 system.

1. `index`: Executes approximately 2.79 million times per second.
2. `map`: Executes approximately 462,592 times per second.

In summary, using `Array.prototype.findIndex` is significantly faster than using `Array.prototype.map` for this specific use case, likely due to the optimized implementation of `findIndex` and the fact that it only scans the array once to find the index.

Related benchmarks:

reassigning an object with larger arrray (version: 0)

Comparing performance of: index vs map

Created: 2 years ago by: Guest

Jump to the latest result

index

map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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