Benchmark: new array vs array.length = 0

Tests:

new array
let a = [0, 1, 2, 3] a = []
array.length = 0
let a = [0, 1, 2, 3] a.length = 0

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
new array
array.length = 0

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/119.0.0.0 Safari/537.36 Edg/119.0.0.0

Browser/OS: Chrome 119 on Windows

View result in a separate tab

Test name	Executions per second
new array	1445158144.0 Ops/sec
array.length = 0	43219148.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the explanation into smaller, manageable parts.

**Benchmark Definition JSON and Benchmark Preparation Code**

The benchmark definition JSON provides essential metadata about the test case:

*   `Name`: The name of the test case (e.g., "new array vs array.length = 0").
*   `Description` and `Html Preparation Code`: These fields are empty in this example, indicating that no description or HTML setup is required for the benchmark.
*   `Script Preparation Code`: Also empty, suggesting that there's no script preparation needed before running the test.

**Individual Test Cases**

Two individual test cases are defined:

1.  **"new array"`**: This test case measures the time it takes to create a new JavaScript array using the syntax `let a = [0, 1, 2, 3]\r\na = []`. The purpose of this test is likely to evaluate how JavaScript engines execute array literals and how they handle reassignments.
2.  **"array.length = 0"`**: This test case measures the time it takes to set the `length` property of an existing array to zero using the syntax `let a = [0, 1, 2, 3]\r\na.length = 0`. The goal here is probably to assess how JavaScript engines handle changes to an array's size and how they optimize this operation.

**Library Used in Test Cases**

There are no libraries explicitly mentioned in these test cases. However, when running a benchmark like this, it's common to use a library that can dynamically create arrays or modify their sizes. Some popular choices include:

*   `Array.from()`
*   `Array.prototype.splice()`
*   `Array.prototype.fill()`

**Special JavaScript Features/Syntax**

The test cases don't utilize any special JavaScript features or syntax. The focus is on measuring the execution time of simple array operations.

**Other Alternatives**

If you wanted to create similar benchmarks, here are some alternatives:

1.  **Measure the execution time of `Array.prototype.slice()` vs. `Array.prototype.subarray()`:**
    *   Measure how JavaScript engines compare these two methods for creating a shallow copy of an array.
2.  **Compare the performance of different array initialization methods:**
    *   Create benchmarks for initializing arrays using `Array.from()`, `Array.from(new Int32Array())`, or other methods, to evaluate their performance and any differences in optimization strategies between browsers.

**Additional Considerations**

When creating benchmarks like this, keep the following points in mind:

*   **Keep it simple:** Start with basic operations and gradually move on to more complex scenarios.
*   **Test a variety of inputs:** Ensure that your benchmark covers different types of input data (e.g., empty arrays, large arrays, arrays with different element types).
*   **Use multiple browsers and platforms:** Running benchmarks across various browsers and devices can help identify platform-specific differences in performance.

By following these guidelines, you can create accurate and informative benchmarks that provide valuable insights into JavaScript engine behavior.

Related benchmarks:

new array vs array.length = 0 (version: 0)

Comparing performance of: new array vs array.length = 0

Created: one year ago by: Registered User

Jump to the latest result

new array

array.length = 0

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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