Benchmark: clearing array via pop() vs shift() vs .length = 0 vs = []1

Script Preparation code:

var array = [];

for(var i = 0; i < 1000; i++){array.push(Math.random());}

Tests:

pop
while (array.length > 0) { array.pop(); }
shift
while (array.length > 0) { array.shift(); }
.splice(0)
array.splice(0);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
pop
shift
.splice(0)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.70 Safari/537.36

Browser/OS: Chrome 92 on Windows

View result in a separate tab

Test name	Executions per second
pop	15359872.0 Ops/sec
shift	15304041.0 Ops/sec
.splice(0)	11050523.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Definition**

The benchmark definition JSON represents a test case that compares three different approaches to clear an array:

1. `pop()`: removing elements from the end of the array using `array.pop()`.
2. `shift()`: removing elements from the beginning of the array using `array.shift()`.
3. `.length = 0` (or equivalently, `array.length = 0`): setting the length property of the array to 0, effectively clearing it.
4. `= []1` (or equivalently, `var array = []1;`): creating a new array and assigning it to the original variable name, effectively overwriting the original array.

**Options Compared**

The three approaches are compared in terms of performance, which is measured by the number of executions per second.

**Pros and Cons**

Here's a brief overview of each approach:

* `pop()`: This method has the advantage of being efficient because it only removes elements from the end of the array, without having to shift or copy all previous elements. However, it's not suitable for arrays with elements at both ends.
* `shift()`: Similar to `pop()`, this method only removes elements from the beginning of the array and is efficient in terms of performance. However, it's also not ideal for arrays with elements at both ends.
* `.length = 0` and `= []1`: These approaches are more straightforward but may have additional overhead due to object property modifications or array creation, respectively.

**Library Usage**

There is no explicit library usage in this benchmark definition. However, the benchmark code assumes that the `array` variable is already defined before running the test cases.

**Special JS Feature/Syntax**

None of the test cases explicitly use any special JavaScript features or syntax beyond standard language elements (e.g., variables, loops).

**Other Alternatives**

If you wanted to explore other approaches for clearing an array in JavaScript, here are a few alternatives:

* `splice(0)`: Similar to `.length = 0`, this method creates a new array and assigns it to the original variable name.
* `slice()`: Instead of using `pop()` or `shift()`, you could use `array.slice(0)` to create a new array with no elements.
* `fill()` and `clear()`: These methods are not as common, but they can be used to clear an array: `array.fill(0, 0, array.length)`

Please note that these alternatives may have different performance characteristics or use more memory, depending on the specific implementation.

**Benchmark Preparation Code**

The benchmark preparation code creates a new empty array and populates it with random numbers using a loop. This ensures that the test cases start with an array of the same size and content for each iteration.

```javascript
var array = [];
for (var i = 0; i < 1000; i++) {
    array.push(Math.random());
}
```

I hope this explanation helps!

Related benchmarks:

clearing array via pop() vs shift() vs .length = 0 vs = []1 (version: 0)

Comparing performance of: pop vs shift vs .splice(0)

Created: 3 years ago by: Guest

Jump to the latest result

pop

shift

.splice(0)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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