Benchmark: empty an array in JavaScript and then reassign again

Tests:

Just instantiate new array
let arr1 = ["a", "b", "c", "d", "e", "f"]; arr1 = [1,2,3,4,5];
Set length to zero
const arr2 = ["a", "b", "c", "d", "e", "f"]; arr2.length = 0; arr2.push(1,2,3,4,5)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Just instantiate new array
Set length to zero

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Just instantiate new array	99094184.0 Ops/sec
Set length to zero	18150330.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared, and the pros and cons of each approach.

**Benchmark Description**

The benchmark is designed to measure how efficiently JavaScript arrays can be emptied and reassigned. There are two test cases:

1. **Just instantiate new array**: This test creates a new array with some elements and then assigns it to a variable.
2. **Set length to zero**: This test sets the length of an existing array to 0 and then pushes new elements into it.

**Comparison of Approaches**

There are two main approaches being compared:

1. **Creating a new array**: In this approach, a new array is created with the desired number of elements, and then assigned to a variable. This method creates a new object in memory and copies the data from the original array.
2. **Modifying an existing array**: In this approach, the length of an existing array is set to 0, and then new elements are pushed into it using the `push()` method.

**Pros and Cons**

1. **Creating a new array**:
	* Pros: Fast and efficient, as it avoids modifying an existing array.
	* Cons: Creates a new object in memory, which can be slower for large arrays due to garbage collection.
2. **Modifying an existing array**:
	* Pros: More memory-efficient, as it modifies the original array instead of creating a new one.
	* Cons: Slower than creating a new array, especially when dealing with large arrays.

**Library and Special JS Features**

There is no library being used in this benchmark. However, it's worth noting that some browsers may use their own optimization techniques or caching mechanisms to improve performance.

**Other Considerations**

1. **Array creation overhead**: The process of creating a new array can incur additional overhead due to the need to allocate memory and perform other internal operations.
2. **Garbage collection**: When using the "Create new array" approach, garbage collection may be triggered more frequently, leading to slower performance.

**Alternative Approaches**

Some alternative approaches that could be explored in this benchmark include:

1. **Using `Array.prototype.fill()` instead of `push()```**: This method can be faster for large arrays, as it avoids the overhead of multiple push operations.
2. **Using a library like Lodash's `cloneDeep()` function**: This function creates a deep clone of an array, which could provide more accurate results in terms of memory usage and performance.

However, these alternative approaches may not be relevant to the specific use case or requirements of this benchmark.

Overall, the benchmark provides a good starting point for understanding how different approaches can affect JavaScript array manipulation. By analyzing the results, developers can gain insights into the trade-offs between creating new arrays versus modifying existing ones.

Related benchmarks:

empty an array in JavaScript and then reassign again (version: 0)

Based on question on http://stackoverflow.com/questions/1232040/how-do-i-empty-an-array-in-javascript

Comparing performance of: Just instantiate new array vs Set length to zero

Created: 2 years ago by: Guest

Jump to the latest result

Just instantiate new array

Set length to zero

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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