Benchmark: clearing array via pop() vs shift() vs .length = 0 vs = [] 2322323

Script Preparation code:

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

Tests:

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

No previous run results

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The benchmark is designed to compare four different approaches for clearing an array:

1. `pop()`: Using `Array.prototype.pop()` to remove and return the last element from the array, repeating this process until the array is empty.
2. `shift()`: Using `Array.prototype.shift()` to remove and return the first element from the array, repeating this process until the array is empty.
3. `length = 0`: Assigning a new value of `0` to the `length` property of the array, effectively clearing it.
4. `a = []`: Reassigning the array to a new empty array using the assignment operator.

**Options Compared**

The benchmark compares the performance of each approach on an array of 1 million elements, populated with random numbers.

**Pros and Cons of Each Approach**

1. **`pop()`**: This approach has the advantage of being simple and straightforward, but it can be slow because `Array.prototype.pop()` needs to iterate through the entire array to find the last element.
2. **`shift()```**: Similar to `pop()`, this approach requires iterating through the entire array to find the first element, making it slower than other methods.
3. **`length = 0```**: This approach is likely to be the fastest because it only involves updating a single property of the array, without requiring any iteration or mutation of the underlying data structure.
4. **`a = []```**: While this approach may seem simple, it can have performance implications due to the creation of a new array object, which requires memory allocation and copying of elements.

**Special JS Features/Syntax**

None mentioned in the benchmark definition.

**Library Usage**

No libraries are used in the benchmark definition. The script preparation code only uses built-in JavaScript features and the `array` variable is created using `var`.

**Other Alternatives**

If you're interested in exploring other approaches, consider:

1. Using `Array.prototype.fill()` with a value of `0`, which would clear the array by setting all elements to zero.
2. Using a custom function or library for array manipulation, such as Lodash's `_.cloneDeep()` and `_.fill()` methods.
3. Utilizing modern JavaScript features like `flatMap()` or `filter()` in combination with array literals or spread operators (`[...array]`) to create a new array.

Keep in mind that the performance of these alternatives may vary depending on the specific use case, hardware, and browser version.

MeasureThat.net's benchmark is designed to help developers compare the performance of different approaches for common JavaScript tasks. By understanding the pros and cons of each approach, you can make informed decisions about which method to use in your own projects.

Related benchmarks:

clearing array via pop() vs shift() vs .length = 0 vs = [] 2322323 (version: 0)

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

Created: 4 years ago by: Guest

Jump to the latest result

pop

shift

length

reassignment

.splice(0)

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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