Benchmark: clearing array via pop() vs shift() vs .length = 0 vs = [] 2322

Script Preparation code:

var array = [];

for(var i = 0; i < 1000000; i++){array.push(Math.random());}

Tests:

pop
while (array.length > 0) { array.pop(); }
shift
while (array.length > 0) { array.shift(); }
length
array.length = 0
reassignment
array = []
.splice(0)
array.splice(0);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
pop
shift
length
reassignment
.splice(0)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:98.0) Gecko/20100101 Firefox/98.0

Browser/OS: Firefox 98 on Windows

View result in a separate tab

Test name	Executions per second
pop	134721888.0 Ops/sec
shift	801611904.0 Ops/sec
length	43147208.0 Ops/sec
reassignment	47061336.0 Ops/sec
.splice(0)	18003854.0 Ops/sec

Autogenerated LLM Summary (model llama3.1:latest, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation.

**Benchmark Definition**

The benchmark tests four different ways to clear an array in JavaScript:

1. **pop()**: using the `pop()` method, which removes and returns the last element from the array, until the array is empty.
2. **shift()**: using the `shift()` method, which removes and returns the first element from the array, until the array is empty.
3. **length = 0**: setting the array's length property to 0 directly.
4. **reassignment**: assigning a new, empty array to the variable (`array = []`).
5. **splice(0)**: using the `splice()` method with an index of 0, which effectively removes all elements from the array.

**Library and special JS features**

None are used in this benchmark.

**Options compared**

The benchmark compares the execution speed (measured in executions per second) of each method to clear an array. The results show that:

* `shift()` is the fastest method, with an average execution speed of 134721888.0 executions per second.
* `pop()` comes next, with an average execution speed of 801611904.0 executions per second (note: this is actually slower than the other methods).
* Setting `length = 0` has a moderate execution speed of 43147208.0 executions per second.
* Reassigning `array = []` is significantly slower, with an average execution speed of 18003854.0 executions per second.
* Using `splice(0)` is the slowest method, with an average execution speed of 47061336.0 executions per second.

**Pros and cons**

Here are some pros and cons for each method:

* **pop()**: Pros - simple to implement; Cons - slower than other methods, modifies array in reverse order.
* **shift()**: Pros - fast; Cons - modifies array in a way that might not be desirable (removes the first element).
* `length = 0`: Pros - simplest and most efficient way to clear an array; Cons - may have performance issues if used with large arrays.
* `reassignment`: Pros - no overhead; Cons - can lead to unexpected behavior if not handled properly.
* **splice(0)**: Pros - easy to implement; Cons - slow, may have issues with large arrays.

**Other considerations**

When choosing a method to clear an array, consider the following:

* If you need to maintain the original order of elements, use `pop()` or `shift()`.
* If performance is critical and you're working with small arrays, use `length = 0` or reassignment.
* Avoid using `splice(0)` unless you have a specific reason for doing so.

**Alternatives**

If you need to clear an array frequently, consider these alternatives:

* Use a more efficient data structure, such as a linked list or a map.
* Implement a custom clearing method that suits your specific needs.
* Consider using a library like Lodash or Underscore.js, which provides optimized functions for common operations.

Related benchmarks:

clearing array via pop() vs shift() vs .length = 0 vs = [] 2322 (version: 0)

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

Created: 2 years ago by: Guest

Jump to the latest result

pop

shift

length

reassignment

.splice(0)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.1:latest, generated 2 months ago):