Benchmark: Add item to first position in array

Script Preparation code:

var array = Array.from(Array(100).keys());
var newElement = 888

Tests:

Unshift
array.unshift(newElement)
Concat
array = [newElement].concat(array)
Spread
array = [newElement, ...array]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Unshift
Concat
Spread

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36

Browser/OS: Chrome 84 on Windows

View result in a separate tab

Test name	Executions per second
Unshift	34551.7 Ops/sec
Concat	987.8 Ops/sec
Spread	189.2 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested, compared, and some pros and cons of different approaches.

**Benchmark Definition**

The benchmark definition represents a JavaScript microbenchmark that tests the performance of adding an item to the first position in an array. The script preparation code initializes an array with 100 elements from 0 to 99 using `Array.from(Array(100).keys())` and assigns a new value `newElement = 888` to a variable.

**Test Cases**

The benchmark has three test cases:

1. **Unshift**: This test case uses the built-in `unshift()` method to add the new element to the beginning of the array.
2. **Concat**: This test case uses the `concat()` method to concatenate an array with a single-element array containing the new element, and then assigns the result back to the original array.
3. **Spread**: This test case uses the spread operator (`...`) to add the new element to the beginning of the array.

**Library and Purpose**

None of these test cases rely on any external libraries.

**Special JS Feature/Syntax**

There's no special JavaScript feature or syntax being used in these test cases. They are using standard methods and operators available in modern JavaScript.

**Pros and Cons of Different Approaches**

1. **Unshift**:
	* Pros: Most efficient way to add an element to the beginning of an array.
	* Cons: May not be supported in older browsers or versions of JavaScript that don't have the `unshift()` method.
2. **Concat**:
	* Pros: Works in all modern browsers and versions of JavaScript, but may incur additional overhead due to the concatenation process.
	* Cons: Less efficient than `unshift()`.
3. **Spread**:
	* Pros: Also works in all modern browsers and versions of JavaScript, but may have performance implications due to the spread operator's complexity.
	* Cons: Less efficient than both `unshift()` and `concat()`, but a good alternative if you want to explore other methods.

**Other Alternatives**

If you wanted to test other approaches for adding an element to the beginning of an array, you could consider:

* Using `Array.prototype.push()`: This would be less efficient than `unshift()` due to the need to shift elements after inserting a new one.
* Using `Array.prototype.splice()`: This would also be less efficient than `unshift()`, as it involves more operations and checks.

Keep in mind that these alternatives may not be supported in older browsers or versions of JavaScript, so make sure to test them thoroughly if you decide to use them.

Related benchmarks:

Add item to first position in array (version: 0)

Comparing performance of: Unshift vs Concat vs Spread

Created: 4 years ago by: Guest

Jump to the latest result

Unshift

Concat

Spread

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):