Benchmark: Speed test1 - MeasureThat.net

Tests:

fill
let a = [1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,2,3,5,6,7,5,4,3]; let b = Array(a.length).fill("");
map
let a = [1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,2,3,5,6,7,5,4,3]; let b = a.map(() => "");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
fill
map

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The MeasureThat.net benchmark measures the performance of two approaches for creating an array with all values equal to an empty string: using `Array.fill()` (the "fill" test case) and using `Array.map()` (the "map" test case).

**Test Case 1: Fill**

In this test case, a large array `a` is created with 44 elements, and then another array `b` is created with the same length using `Array.fill()`, filling all elements with an empty string `"`. The benchmark measures how long it takes to execute this code.

**Test Case 2: Map**

In this test case, a large array `a` is created with 44 elements (same as above), and then another array `b` is created by applying the `map()` function to each element in `a`, which returns an empty string `"`. The benchmark measures how long it takes to execute this code.

**Comparison of Approaches**

1. **Array.fill()**
	* Pros:
		+ Generally faster than `map()` for large arrays, since it uses a single, optimized loop.
		+ Can be more cache-friendly, as the entire array is filled at once.
	* Cons:
		+ May not work correctly if the array length changes dynamically, since `fill()` only works with fixed lengths.
2. **Array.map()**
	* Pros:
		+ More flexible than `fill()`, as it can be used to transform each element in an array without creating a new array.
		+ Can handle dynamic array lengths, but may incur more overhead due to the function call and iteration.
	* Cons:
		+ May be slower than `fill()` for very large arrays, since it involves multiple loop iterations.

**Library/Features Used**

None of the test cases explicitly use a library or special JavaScript features. However, some browsers may implement additional optimizations or behavior that could affect the results.

**Other Alternatives**

If you wanted to create an array with all values equal to an empty string, there's also the `Array.prototype.fill()` method with a different signature:
```javascript
const b = new Array(a.length).fill(''); // using constructor syntax
```
Alternatively, you could use the spread operator (`...`) to create a new array with repeated elements:
```javascript
const b = [...new Array(a.length).keys()].map(() => ''); // using spread and map
```
However, these approaches are not specifically tested in this benchmark.

**Considerations**

When choosing between `Array.fill()` and `Array.map()`, consider the specific requirements of your use case:

* If you need to transform each element in an array, `map()` is likely a better choice.
* If you need to create a new array with all elements equal to a specific value, `fill()` might be faster and more efficient.

Keep in mind that performance differences between these approaches can vary depending on the browser, JavaScript engine, and specific use case. MeasureThat.net provides a helpful platform for comparing different approaches and identifying potential performance bottlenecks.

Related benchmarks:

Speed test1 (version: 0)

create an array with all values "" same length than the original array

Comparing performance of: fill vs map

Created: 7 years ago by: Guest

Jump to the latest result

fill

map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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