Benchmark: filling - MeasureThat.net

Script Preparation code:

var n = 1000;
var arr;

Tests:

1
for(var i=n-1, arr=[i]; i--; arr.unshift(i));
2
const arr = Array(n).fill().map((_,i)=>i)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
1
2

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

I'd be happy to explain the benchmark and its options.

The provided JSON represents a JavaScript microbenchmark on MeasureThat.net, which is designed to compare different approaches for creating an array in JavaScript.

**Benchmark Definition:**

The benchmark definition includes two test cases:

1. `for(var i=n-1, arr=[i]; i--; arr.unshift(i));`
2. `const arr = Array(n).fill().map((_,i)=>i)`

These two test cases are designed to create an array of size `n` using different approaches.

**Options Compared:**

The benchmark compares the performance of two options:

1. **Manual array creation with a for loop**: This approach creates an array by manually iterating over the range from 0 to `n-1`, and then uses the `unshift()` method to add each element to the end of the array.
2. **Using the Array constructor with fill() and map()**: This approach uses the `Array` constructor, which is a built-in JavaScript function that creates an empty array. The `fill()` method is used to populate the array with `n` elements, and then the `map()` method is used to create a new array with the desired elements.

**Pros and Cons:**

**Manual Array Creation with a for loop:**

Pros:

* Simple and easy to understand
* No additional libraries or dependencies required

Cons:

* Can be slow and inefficient due to the use of the `unshift()` method, which has to shift all elements in the array
* May not handle edge cases well, such as when the input size is very large

**Using the Array constructor with fill() and map():**

Pros:

* Fast and efficient, especially for larger inputs
* Handles edge cases well, since the `Array` constructor is designed to handle a wide range of input sizes

Cons:

* Requires the use of built-in JavaScript functions, which may not be familiar to some developers
* May require more memory to create the intermediate arrays used by `fill()` and `map()`

**Other Considerations:**

* The benchmark uses a large input size (`n = 1000`) to ensure that any performance differences are significant.
* The use of `const` and `let` keywords for variable declarations is not mentioned in the benchmark definition, but it's worth noting that these keywords can affect the behavior of JavaScript code.

**Library/External Function:**

The library used here is none.

Latest run results:

Run details: (Test run date: 2025 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.119 Safari/537.36

Browser/OS: Chrome 64 on Linux

View result in a separate tab

Test name	Executions per second
1	9023.4 Ops/sec
2	52418.3 Ops/sec

Related benchmarks:

filling (version: 0)

Comparing performance of: 1 vs 2

Created: 6 years ago by: Guest

Jump to the latest result

1

2

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):