Benchmark: empty an array in JavaScript?

Tests:

Just instantiate new array
var size = 10000; var arr1 = []; for (var i = 0; i < size; i++){ arr1.push(i); } arr1 = [];
Set length to zero
var size = 10000; var arr2 = []; for (var i = 0; i < size; i++){ arr2.push(i); } arr2.length = 0;
Splice
var size = 10000; var arr3 = []; for (var i = 0; i < size; i++){ arr3.push(i); } arr3.splice(0, arr3.length);
Pop all values
var size = 10000; var arr4 = []; for (var i = 0; i < size; i++){ arr4.push(i); } while(arr4.length > 0){ arr4.pop(); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Just instantiate new array
Set length to zero
Splice
Pop all values

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Windows

View result in a separate tab

Test name	Executions per second
Just instantiate new array	25365.4 Ops/sec
Set length to zero	24904.5 Ops/sec
Splice	22728.0 Ops/sec
Pop all values	15560.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**What is tested?**

The provided benchmark tests four different approaches to empty an array in JavaScript:

1. Instantiating a new, empty array (`arr1 = []`).
2. Setting the length of an existing array to zero (`arr2.length = 0`).
3. Using the `splice(0, arr3.length)` method to remove all elements from an array (`arr3.splice(0, arr3.length)`).
4. Popping all values from an array using a while loop (`while(arr4.length > 0){ arr4.pop();}`).

**Options comparison**

Here's a brief overview of each approach and its pros and cons:

1. **Instantiating a new array**: This method is simple and efficient, as it involves creating a new object and assigning it to the variable `arr1`. However, it requires more memory allocation compared to other methods.
2. **Setting length to zero**: This method is also straightforward and doesn't require any additional memory allocation. However, it can be slower than instantiating a new array because it needs to update the internal length property of the array object.
3. **Splice**: Using `splice(0, arr3.length)` removes all elements from the array by updating the internal length property. This method is similar to setting the length to zero but uses a different API. It can be slower than instantiating a new array because it needs to perform additional operations on the array object.
4. **Pop all values**: Using a while loop to pop all values from an array is the most memory-intensive approach, as it involves repeatedly calling the `pop()` method and discarding the returned value.

**Library usage**

None of the provided benchmark definitions uses any external libraries or frameworks.

**Special JS feature or syntax**

There are no special JavaScript features or syntax used in these benchmark definitions. The code is written in plain JavaScript and follows standard syntax and semantics.

**Other alternatives**

If you're interested in exploring alternative approaches to emptying an array, here are a few more options:

* Using `fill()` method: `arr5.fill(0);` would clear the array by filling it with zeros.
* Using `map()` method with an identity function: `arr6.map(() => 0);` would create a new array with all elements set to zero and then discard the original array.
* Using `reduce()` method with an identity function: `arr7.reduce((a, b) => a + b, 0);` would create a new array with the sum of all elements and then discard the original array.

Keep in mind that these alternatives may have different performance characteristics compared to the original benchmark definitions.

Related benchmarks:

empty an array in JavaScript? (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 vs Splice vs Pop all values

Created: 8 years ago by: Registered User

Jump to the latest result

Just instantiate new array

Set length to zero

Splice

Pop all values

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):