Benchmark: Spread Operator vs. Unshift()

Script Preparation code:

var arr = ['', '', ''];

Tests:

Spread
arr = [27, ...arr];
Unshift()
arr.unshift(27);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Unshift()

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36

Browser/OS: Chrome 118 on Windows

View result in a separate tab

Test name	Executions per second
Spread	1876.2 Ops/sec
Unshift()	17981.9 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided JSON benchmark data and explain what's being tested, the different approaches compared, their pros and cons, and other considerations.

**Benchmark Definition**

The benchmark is testing two approaches: using the spread operator (`...`) to add elements to an array versus using the `unshift()` method. The benchmark definition is:

1. Using the spread operator: `arr = [27, ...arr];`
2. Using `unshift()`: `arr.unshift(27);`

**Script Preparation Code**

The script preparation code initializes an empty array `arr` with three elements.

**Html Preparation Code**

There is no HTML preparation code provided, which suggests that the benchmark only tests JavaScript performance and does not consider any DOM-related factors.

**Individual Test Cases**

There are two test cases:

1. "Spread": This test case uses the spread operator to add an element (27) to the beginning of the `arr` array.
2. "Unshift()": This test case uses the `unshift()` method to add an element (27) to the beginning of the `arr` array.

**Library and Purpose**

Neither of these approaches requires a specific library, as they are built-in JavaScript methods.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax being used in these test cases. The spread operator and `unshift()` method are standard parts of the JavaScript language.

**Pros and Cons of Different Approaches**

1. **Spread Operator (`...`)**:
	* Pros: Efficient and concise way to add elements to an array, creates a new array instead of modifying the existing one.
	* Cons: May have performance overhead due to the creation of a new array, depending on the JavaScript engine and implementation.
2. **Unshift()**:
	* Pros: Modifies the existing array in place, which can be more efficient than creating a new array.
	* Cons: Can be less readable and maintainable than using the spread operator, as it modifies the original array.

**Other Considerations**

The benchmark is likely designed to test performance differences between these two approaches. However, the actual performance impact may vary depending on specific use cases and JavaScript engine implementations. It's also worth noting that the spread operator can be useful in other scenarios beyond simply adding elements to an array.

**Alternatives**

If you were to design a similar benchmark, you might consider testing additional approaches or variations, such as:

* Using `concat()` instead of the spread operator
* Comparing performance with different JavaScript engines (e.g., V8 vs. SpiderMonkey)
* Testing performance on smaller or larger arrays
* Incorporating additional factors like array size and data type (e.g., string vs. number)

Keep in mind that these alternatives would require modifying the benchmark definition and test cases to reflect the new scenarios being tested.

Related benchmarks:

Spread Operator vs. Unshift() (version: 0)

Comparing performance of: Spread vs Unshift()

Created: 2 years ago by: Guest

Jump to the latest result

Spread

Unshift()

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):