Benchmark: spread vs concat vs unshift vs slice.unshift

Script Preparation code:

var array = [1,2,3];

Tests:

arrayUnshift123C
array.unshift(0);
arrayConcat123C
array = array.concat([0])
arraySpread123C
array = [0, ...array]
arraySliceUnshift123C
array.slice().unshift(0);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arrayUnshift123C
arrayConcat123C
arraySpread123C
arraySliceUnshift123C

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36

Browser/OS: Chrome 112 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
arrayUnshift123C	10154.3 Ops/sec
arrayConcat123C	622.2 Ops/sec
arraySpread123C	149.4 Ops/sec
arraySliceUnshift123C	387.2 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

The provided JSON represents a benchmarking test case on MeasureThat.net, which compares the performance of different array manipulation methods in JavaScript: `unshift`, `concat`, `spread` (via rest parameter syntax), and `slice.unshift`.

**Benchmark Definition**

The benchmark definition is represented by two parts:

1. **Script Preparation Code**: The code that initializes an array with three elements (`var array = [1,2,3];`) before each test case.
2. **Html Preparation Code**: An empty string, indicating that no additional HTML preparation is required.

**Individual Test Cases**

Each test case represents a specific scenario:

1. `array.unshift(0);`: Pushes the element 0 onto the end of the array using `unshift`.
2. `array = array.concat([0])`: Creates a new array by concatenating the original array with an array containing the element 0.
3. `array = [0, ...array]`: Spreads the elements of the original array after the initial element 0 using rest parameter syntax.
4. `array.slice().unshift(0)`: Slices the original array to create a new slice, and then uses `unshift` on that slice.

**Options Compared**

The benchmark compares the performance of four different methods:

1. `unshift`
2. `concat`
3. `spread` (via rest parameter syntax)
4. `slice.unshift`

**Pros and Cons of Each Approach**

Here's a brief overview of each approach:

1. **`unshift`**: This method has an average time complexity of O(n), making it inefficient for large arrays.
2. **`concat`**: This method also has an average time complexity of O(n) but is slightly faster than `unshift` due to its optimized implementation.
3. **`spread` (rest parameter syntax)**: This approach uses a rest parameter (`...array`) to spread the elements, which is more efficient than concatenating or using `slice.unshift`.
4. **`slice.unshift`**: This method slices the original array and then uses `unshift`, which can be slower than the other methods due to the additional operation.

**Library and Special JS Features**

None of the provided test cases use any external libraries. However, they do utilize special JavaScript features:

1. Rest parameter syntax (`...array`) is used in the `array = [0, ...array]` test case.
2. The `concat` method uses a non-standard implementation on some browsers.

**Other Alternatives**

Some alternative methods could be explored for comparison, such as:

1. Using `splice` instead of `unshift`
2. Utilizing `Array.prototype.push()` and `Array.prototype.length`
3. Implementing custom array manipulation functions

Keep in mind that the choice of alternative methods depends on the specific requirements of the benchmark and the performance characteristics of each method.

**Interpretation of Benchmark Results**

The provided results indicate that:

1. The `spread` (rest parameter syntax) approach is the fastest, followed closely by `concat`.
2. `unshift` is slower than both `concat` and `spread`.
3. `slice.unshift` is the slowest due to its additional operation.

This benchmark provides valuable insights into the performance characteristics of different array manipulation methods in JavaScript.

Related benchmarks:

spread vs concat vs unshift vs slice.unshift (version: 0)

spread vs concat vs unshift vs slice.unshift

Comparing performance of: arrayUnshift123C vs arrayConcat123C vs arraySpread123C vs arraySliceUnshift123C

Created: one year ago by: Guest

Jump to the latest result

arrayUnshift123C

arrayConcat123C

arraySpread123C

arraySliceUnshift123C

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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