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

Autogenerated LLM Summary (model gemma2:9b, generated one month ago):

LLMs can make mistakes. Check important info.

This benchmark on MeasureThat.net compares five different methods for clearing an array in JavaScript:

**Methods:**

1. **`pop()`**: Removes the last element of the array repeatedly until it's empty. 
2. **`shift()`**: Removes the first element of the array repeatedly until it's empty.
3. **`array.length = 0`**: Sets the length property of the array to zero, effectively removing all elements.
4. **`array = []`**: Assigns a new empty array to the same variable name, essentially replacing the old array with a new one. This doesn't modify the original array in place.
5. **`.splice(0)`**: Removes elements from the beginning of the array using the `splice()` method with an index of 0.

**Pros and Cons:**

* **`pop()`**: Generally efficient for removing elements from the end, but might be slower for clearing the entire array compared to other methods.
* **`shift()`**: Similar to `pop()`, efficient for removing elements from the beginning, but slower for clearing the entire array.
* **`array.length = 0`**:  Often considered the most performant method for clearing an array as it directly modifies the length property without iterating through elements.
* **`array = []`**: Creates a new array in memory, which can be inefficient for large arrays as it involves copying all elements to a new location. Not an in-place modification.
* **`.splice(0)`**:  Can be more verbose and potentially less efficient than `array.length = 0` for clearing the entire array.

**Other Considerations:**

* **Memory Usage:** Methods like `pop()`, `shift()`, and `.splice(0)` modify the original array in place, while methods like `reassignment` create a new array, potentially consuming more memory.
* **Readability:** Some methods might be more readable depending on the context and programmer preference.

**Alternatives:**

There are no significant alternatives to clearing an array in JavaScript besides the methods mentioned.

Remember that benchmark results can vary based on factors like browser implementation, hardware, and other running processes. It's best to consider these results as general guidelines rather than absolute truths.

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

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 gemma2:9b, generated one month ago):