Benchmark: splice() vs copyWithin() for adding element at index

Tests:

splice()
for (var k = 0; k < 100; k++) { var arr = new Array(1000); for (var j = 0; j < arr.length; j++) arr[j] = Math.random(); arr.splice(5, 0, 'test'); }
copyWithin()
for (var k = 0; k < 100; k++) { var arr = new Array(1000); for (var j = 0; j < arr.length; j++) arr[j] = Math.random(); arr.length++; arr.copyWithin(6, 5); arr[5] = 'test'; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
splice()
copyWithin()

Fastest: N/A

Slowest: N/A

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

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Let's break down the provided benchmark and explain what's being tested, compared options, pros and cons, and other considerations.

**Benchmark Overview**

The benchmark compares the performance of two methods for adding an element at a specific index to an array: `splice()` and `copyWithin()`. The benchmark consists of two individual test cases:

1. **`splice()`**: This test case generates an array of 1000 elements, fills it with random values, and then uses `splice()` to add an element at the 6th index.
2. **`copyWithin()`**: This test case generates an array of 1000 elements, fills it with random values, and then increments the length of the array by 1 before using `copyWithin()` to copy elements from the new starting index (5) to the original starting index (6), while overwriting the element at the 5th index.

**Libraries Used**

Neither `splice()` nor `copyWithin()` use any external libraries. These are built-in JavaScript methods.

**Special JS Features/Syntax**

There's no special JavaScript feature or syntax being used in these benchmark tests.

**Options Compared**

The two options being compared are:

1. **`splice()`**: This method modifies the original array by removing and/or replacing existing elements. It has a time complexity of O(n), where n is the number of elements being inserted or deleted.
2. **`copyWithin()`**: This method creates a new subset of an array, copying elements from one section to another. Its time complexity depends on the length of the array segment being copied.

**Pros and Cons**

**`splice()`**:

Pros:

* Simpler implementation
* Fewer overhead operations compared to `copyWithin()`

Cons:

* Time complexity is O(n) due to potential removals or modifications, which can be slower for large arrays.
* Can be less predictable in terms of performance since it may require additional operations.

**`copyWithin()`**:

Pros:

* More efficient time complexity, especially when only a subset of elements needs to be copied.
* Predictable and consistent performance due to its deterministic nature.

Cons:

* May incur higher overhead costs for creating a new array segment.
* Limited flexibility in terms of modifying the original array structure.

**Other Considerations**

When choosing between `splice()` and `copyWithin()`, consider the specific use case:

* If you need to insert or delete elements frequently, `splice()` might be more suitable due to its simplicity. However, its time complexity may outweigh performance benefits.
* For copying smaller subsets of an array or when predictability is crucial, `copyWithin()` is a better choice.

**Alternative Approaches**

Other methods for adding an element at a specific index in an array could include:

1. **Using the `at` method (ES6+)**: This method provides direct access to elements by their index and can be more efficient than using `splice()` or `copyWithin()`.
2. **Creating a new array**: Instead of modifying the original array, creating a new one with the desired element at the specified index.
3. **Using a library or utility function**: Depending on the specific requirements, specialized libraries or utility functions might offer optimized implementations for these operations.

Keep in mind that these alternatives may have different performance characteristics and trade-offs depending on your use case.

Related benchmarks:

splice() vs copyWithin() for adding element at index (version: 0)

Comparing performance of: splice() vs copyWithin()

Created: 4 years ago by: Guest

Jump to the latest result

splice()

copyWithin()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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