Benchmark: length = 0 vs reassignment

Tests:

Set length to 0
const arr = []; for (let i = 0; i < 10000; i++) { for (let j = 0; j < 100; j++) { arr.push(i); } arr.length = 0; };
Reassign the array
let arr = []; for (let i = 0; i < 10000; i++) { for (let j = 0; j < 100; j++) { arr.push(i); } arr = []; };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Set length to 0
Reassign the array

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark is designed to compare two approaches for resetting an array in JavaScript: setting its length to 0 versus reassigning it using the assignment operator.

**Benchmark Definition**

The benchmark definition specifies the following:

*   Two test cases:
    *   "Set length to 0": This test case creates an array, pushes 10,000 elements into it, and then sets its length to 0.
    *   "Reassign the array": This test case is similar to the previous one but uses the assignment operator `arr = []` instead of setting the length to 0.

**Options Compared**

The benchmark compares two approaches for resetting an array:

1.  **Setting the length to 0**: This method involves using the `length` property of the array object to reset its size.
2.  **Reassigning the array**: This method involves reassigning the array variable itself to a new empty array, effectively replacing it with a fresh instance.

**Pros and Cons**

Here are some pros and cons of each approach:

*   **Setting the length to 0**
    *   Pros:
        *   Can be more efficient in terms of memory usage since it doesn't create a new object.
        *   Can be faster because it's a simple property access operation.
    *   Cons:
        *   May not work correctly in all environments (e.g., older browsers).
*   **Reassigning the array**
    *   Pros:
        *   Works consistently across different environments.
        *   Creates a new object, which can be beneficial for garbage collection.
    *   Cons:
        *   Can be less efficient in terms of memory usage since it creates a new object.
        *   May be slower due to the assignment operation.

**Library and Special JS Features**

There is no library used in this benchmark. However, the test cases do utilize JavaScript's built-in `Array` prototype and its methods (e.g., `push`, `length`).

No special JavaScript features are mentioned in the benchmark definition or individual test cases.

**Alternatives**

If you're interested in exploring alternative approaches for resetting an array, here are a few options:

*   **Using `splice()`**: Instead of setting the length to 0 or reassigning the array, you could use `splice(0, arr.length)` to remove all elements from the array. This method is more efficient than creating a new array but may not be suitable for all use cases.
*   **Using `concat()```**: Another approach is to concatenate an empty array with the original one using `arr = arr.concat([])`. However, this method creates a new object and may have performance implications.

These alternatives can be used in different scenarios depending on your specific requirements and constraints.

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 13; Pixel 7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 107 on Android

View result in a separate tab

Test name	Executions per second
Set length to 0	219.3 Ops/sec
Reassign the array	230.4 Ops/sec

Related benchmarks:

length = 0 vs reassignment (version: 0)

Comparing performance of: Set length to 0 vs Reassign the array

Created: one year ago by: Guest

Jump to the latest result

Set length to 0

Reassign the array

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):