Benchmark: slice vs splice for inserting object

Script Preparation code:

var events = [];
var virtualEventIndex = 400000
var virtualEvent = { key: 'virtual' }
for (var i = 0; i < 1000000; i++) {
  events.push({ key: i });
}

Tests:

slice
var newEvents = [ ...events.slice(0, virtualEventIndex), virtualEvent, ...events.slice(virtualEventIndex), ]
splice
events.splice(virtualEventIndex, 0, virtualEvent)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
splice

Fastest: N/A

Slowest: N/A

Latest run results:

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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 its test cases.

**Benchmark Purpose:**
The benchmark measures the performance difference between two approaches for inserting an object into an array:

1. `Array.prototype.slice()`: creates a shallow copy of the original array, and then uses this new array to insert the object.
2. `Array.prototype.splice()`: modifies the original array in-place, shifting all elements after the insertion point to the right.

**Options Compared:**
The benchmark compares these two approaches:

* **Slice**: Creates a new array using `slice()` and inserts the object into it.
* **Splice**: Modifies the original array using `splice()` and inserts the object at a specified index.

**Pros and Cons of Each Approach:**

* **Slice**:
	+ Pros: creates a new, independent copy of the array, which can be useful in certain situations (e.g., when preserving the original data).
	+ Cons: requires extra memory allocation, copying, and potentially slower performance due to the overhead of creating a new array.
* **Splice**:
	+ Pros: modifies the original array in-place, which can lead to faster performance since no extra memory is allocated.
	+ Cons: modifies the original array, which might be undesirable if the original data needs to remain intact.

**Library Usage:**
The benchmark uses `Array.prototype.slice()` and `Array.prototype.splice()`, both of which are native JavaScript methods. These methods are part of the ECMAScript standard and are supported by most modern browsers.

**Special JS Feature/Syntax:**
There is no special JS feature or syntax used in this benchmark. The code is straightforward and relies solely on basic JavaScript concepts.

**Benchmark Preparation Code:**
The preparation code creates a large array `events` with 1,000,000 elements, each containing an increasing integer value (`key`). This allows the benchmark to generate a large amount of data for testing.

**Other Alternatives:**

* **Using a library like Lodash**: One could use a utility library like Lodash, which provides a `cloneDeep()` function that creates a deep copy of an array. However, this would add extra dependencies and potentially impact performance.
* **Using `Array.from()`**: Another alternative is to use the `Array.from()` method to create a new array from an iterable (in this case, the original array's elements). While `Array.prototype.slice()` might be slightly faster in some cases, `Array.from()` can provide more flexibility and readability.

Overall, the benchmark provides a simple yet informative comparison of two common array manipulation techniques in JavaScript.

Related benchmarks:

slice vs splice for inserting object (version: 0)

Comparing performance of: slice vs splice

Created: 6 years ago by: Guest

Jump to the latest result

slice

splice

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):