Benchmark: Array padding - MeasureThat.net

Tests:

while loop
const keys = ['a', 'b', 'c', 'd'] const vals = ['1', 'd'] const result = [...vals]; while (result.length < keys.length) { result.push(''); }
Array alloc
const keys = ['a', 'b', 'c', 'd'] const vals = ['1', 'd'] const filler = Array(keys.length - vals.length).fill(''); [...vals].concat(...filler);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
while loop
Array alloc

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:75.0) Gecko/20100101 Firefox/75.0

Browser/OS: Firefox 75 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
while loop	16469752.0 Ops/sec
Array alloc	5107549.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the test cases and explain what is being tested, along with their pros and cons.

**Benchmark Definition**
The benchmark definition specifies that we're testing the performance of JavaScript code related to array padding or allocation.

**Test Cases**

1. **"while loop"`**
This test case measures the performance of using a while loop to pad an array with empty strings until it reaches a specified length.

```javascript
const keys = ['a', 'b', 'c', 'd'];
const vals = ['1', 'd'];
const result = [...vals];
while (result.length < keys.length) {
  result.push('');
}
```

Pros:

* Simple and easy to understand.
* Relatively low memory allocation overhead.

Cons:

* Can lead to a lot of repeated operations (pushing empty strings).
* May not be optimized for performance.

2. **"Array alloc"`**
This test case measures the performance of using `Array.prototype.concat()` with the spread operator (`...`) to pad an array with empty strings until it reaches a specified length.

```javascript
const keys = ['a', 'b', 'c', 'd'];
const vals = ['1', 'd'];
const filler = Array(keys.length - vals.length).fill('');
[...vals].concat(...filler);
```

Pros:

* More efficient than using a while loop, as it avoids repeated operations.
* Can be optimized for performance.

Cons:

* May require additional memory allocation.
* Can lead to cache misses due to the use of `Array.prototype.concat()`.

**Library Used:**
In both test cases, no specific library is used. The code relies solely on built-in JavaScript features.

**Special JS Features/Syntax:**
None are explicitly mentioned. However, note that the use of spread operator (`...`) in the "Array alloc" test case is a modern JavaScript feature introduced in ECMAScript 2015 (ES6).

**Other Alternatives:**

1. **Using `Array.prototype.push()`**: Instead of using a while loop or `Array.prototype.concat()`, you could also use `Array.prototype.push()` to pad the array.

```javascript
const keys = ['a', 'b', 'c', 'd'];
const vals = ['1', 'd'];
while (result.length < keys.length) {
  result.push('');
}
```

This approach is similar to the while loop, but uses a more concise syntax.

2. **Using `Array.prototype.fill()`**: Another alternative is using `Array.prototype.fill()` to create an array of empty strings and then concatenating it with the original array.

```javascript
const keys = ['a', 'b', 'c', 'd'];
const vals = ['1', 'd'];
const filler = Array(keys.length - vals.length).fill('');
[...vals, ...filler];
```

This approach avoids the need for explicit looping or concatenation.

These alternatives can be used to further optimize the performance of array padding.

Related benchmarks:

Array padding (version: 0)

Comparing performance of: while loop vs Array alloc

Created: 4 years ago by: Guest

Jump to the latest result

while loop

Array alloc

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):