Benchmark: Array splice vs array assign

Script Preparation code:

var input = [];
for (var i = 0; i < 50000; i++) {
    input.push({
        id: i,
        data: 'something'
    })
}

Tests:

Array splice
const index = input.findIndex(val => val.id === 999); input.splice(index, 1, {id: 999, data: 'somethingElse'});
Object property assign
const index = input.findIndex(val => val.id === 999); input[index] = {id: 999, data: 'somethingElse'}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array splice
Object property assign

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/145.0.0.0 Safari/537.36 Edg/145.0.0.0

Browser/OS: Chrome 145 on Windows

View result in a separate tab

Test name	Executions per second
Array splice	1160236.5 Ops/sec
Object property assign	1193873.4 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

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The benchmark named "Array splice vs array assign" compares two methods of updating an object within an array in JavaScript: using the `splice` method and using direct assignment of an object property.

### Benchmark Tests
1. **Array splice**:
    ```javascript
    const index = input.findIndex(val => val.id === 999);
    input.splice(index, 1, {id: 999, data: 'somethingElse'});
    ```
   - **Description**: This test first locates the index of the object with `id` 999 using `findIndex`. It then removes that object and inserts a new object at the same index using `splice`.
   - **Pros**: 
     - `splice` can directly modify the original array and is useful for operations where you need to both remove and add an element simultaneously.
     - It can be more readable when performing multiple operations in one step.
   - **Cons**:
     - Involves more operations (removal and addition), which can be slower in larger arrays.
     - Potential performance overhead due to managing array length and re-indexing.

2. **Object property assign**:
    ```javascript
    const index = input.findIndex(val => val.id === 999);
    input[index] = {id: 999, data: 'somethingElse'};
    ```
   - **Description**: This test also finds the index of the object with `id` 999, but it replaces the object at that index directly with a new object.
   - **Pros**:
     - Simpler and potentially faster than `splice` for simply replacing an object, as it only requires accessing the index and changing the value.
     - Avoids the overhead of modifying the array structure.
   - **Cons**:
     - It does not allow for removal of an object in the same operation, which can be a limitation in some scenarios (though unnecessary for this benchmark).

### Performance Results
- The test results indicate that the "Object property assign" method has a higher execution rate (1,420,837 executions per second) compared to "Array splice" (1,379,187 executions per second). This suggests that direct property assignment is generally more performant than splicing in this context.

### Other Considerations
- **Memory Management**: When using `splice`, the underlying implementation might create intermediate arrays or deal with re-allocation, which can be less memory efficient. Direct assignment only replaces a reference, leading to a smaller memory overhead.
- **Readability and Maintainability**: Sometimes, maintainability and readability can be as critical as performance, depending on the size and complexity of your application. The choice between these methods can depend on developer preference and specific application requirements.

### Alternatives
- **Using `map`**: If bulk updates across an array are needed, using `map` can be a more functional approach:
    ```javascript
    input = input.map(val => val.id === 999 ? {id: 999, data: 'somethingElse'} : val);
    ```
   - This creates a new array with updated values without modifying the existing array, and it can be more declarative.
  
- **Using Libraries**: Libraries like **lodash** or **Immutable.js** can manage state updates more efficiently. For instance, Immutable.js helps in maintaining immutability which leads to reliable performance in larger applications.

In summary, the benchmark evaluates two different approaches to updating an array of objects, with performance metrics clearly favoring direct assignment over splice. Each method has its use cases and can be chosen based on specific requirements at hand.

Related benchmarks:

Array splice vs array assign (version: 1)

Comparing performance of: Array splice vs Object property assign

Created: one year ago by: Guest

Jump to the latest result

Array splice

Object property assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):