Benchmark: Array Pop vs setting array length -1

Tests:

Array pop
let array = new Array(100000).fill(0); while (array.length > 0) { array.pop(); }
Array set length
let array = new Array(100000).fill(0); while (array.length > 0) { array.length = array.length - 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array pop
Array set length

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 7 days ago):

LLMs can make mistakes. Check important info.

The benchmark provided compares two different methods for removing elements from an array in JavaScript: using the `Array.prototype.pop()` method versus directly setting the `length` property of the array to truncate it.

### Options Compared

1. **Array Pop**
   - **Test Case Definition:** 
     ```javascript
     let array = new Array(100000).fill(0);
     while (array.length > 0) {
         array.pop();
     }
     ```
   - **Description:** This method utilizes the `pop()` function, which removes the last element from the array and returns that element. The operation is repeated until the array is empty.

2. **Array Set Length**
   - **Test Case Definition:**
     ```javascript
     let array = new Array(100000).fill(0);
     while (array.length > 0) {
         array.length = array.length - 1;
     }
     ```
   - **Description:** This alternative directly manipulates the `length` property of the array. By decreasing the `length` by 1 in each iteration, all elements will be removed effectively.

### Performance Results

From the benchmark results:
- **Array Pop:** Approximately 620 executions per second.
- **Array Set Length:** Approximately 52 executions per second.

### Pros and Cons

#### Array Pop
- **Pros:**
  - Simplicity: The `pop()` method is straightforward and easy to read.
  - Safety: It remains clear that you are sequentially removing elements from the end of the array, which can help in maintaining the intended logic.
- **Cons:**
  - Performance: This approach may incur more overhead compared to setting the length directly, as it processes each element individually.

#### Array Set Length
- **Pros:**
  - Performance: As evidenced by the benchmark results, reducing the length property can dramatically decrease the time complexity when emptying a large array.
  - Efficiency: This method does not involve running through each element, thus doing fewer operations on the underlying array structure.
- **Cons:**
  - Readability: It can be less intuitive for some developers who may not be accustomed to manipulating the `length` property directly.
  - Potential Confusion: If not careful, this approach can lead to unexpected behavior, especially if the array is being accessed elsewhere concurrently.

### Other Considerations

- **Memory Management:** When an array's length is set directly, it may prompt more aggressive garbage collection as the array elements are no longer referenced. The `pop()` method, in contrast, may not clear references until the final element is removed, potentially keeping more memory allocated.

- **Use Case Suitability:** For applications where performance is critical and large arrays are manipulated frequently, using direct length manipulation could be the preferred approach. However, for smaller arrays or one-time operations where readability is more important, `pop()` could be sufficient.

### Alternatives

Apart from these methods, other ways to empty or manipulate arrays include:

1. **Splice Method:**
   - You can use `array.splice(0, array.length)` to remove all elements from the array while maintaining array references and potentially avoiding variable re-assignments.
   
2. **Creating a New Array:**
   - Setting the variable to a new instance, e.g., `array = []`, is another way to empty the array, but it creates a new reference and breaks any other references to the original array.

3. **Using Higher-order Functions:**
   - Depending on the operation, methods like `filter()`, `reduce()`, or `map()` can also be used to remove elements based on specific conditions, albeit not directly for emptying.

In conclusion, the benchmark reveals significant differences in performance between two commonly used methods for emptying arrays. Understanding these trade-offs can help developers choose the most appropriate technique based on their specific context and performance requirements.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Linux

View result in a separate tab

Test name	Executions per second
Array pop	3656.1 Ops/sec
Array set length	388.0 Ops/sec

Related benchmarks:

Array Pop vs setting array length -1 (version: 1)

Comparing array pop vs setting array length

Comparing performance of: Array pop vs Array set length

Created: 8 days ago by: Guest

Jump to the latest result

Array pop

Array set length

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 7 days ago):