Benchmark: JS delete vs undefined vs null

Script Preparation code:

var payload = {}
for (let i = 0; i < 1000; i++) {
  payload[i] = i
}

Tests:

delete
for (let i = 1000; i--;) { delete payload[i] }
undefined
for (let i = 1000; i--;) { payload[i] = undefined }
null
for (let i = 1000; i--;) { payload[i] = null }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
delete
undefined
null

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.5112.102 Safari/537.36

Browser/OS: Chrome 104 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
delete	17536.3 Ops/sec
undefined	8544.2 Ops/sec
null	25873.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases.

**Benchmark Definition:**

The `Script Preparation Code` is used to initialize a JavaScript array (`payload`) with 1000 elements, where each element is assigned a unique integer value from 0 to 999. This preparation code is executed only once before running each individual test case.

**Individual Test Cases:**

There are three test cases:

1. **delete**: The `Benchmark Definition` uses a `for` loop that iterates 1000 times, and within the loop, it calls the `delete` keyword on an array element (`payload[i]`) that is being decremented (i.e., `i--`). This effectively removes each element from the array. The purpose of this test case is to measure the performance impact of deleting an element in an array.
2. **undefined**: Similarly, this test case uses a `for` loop that iterates 1000 times, and within the loop, it assigns `undefined` to an array element (`payload[i]`). This creates a series of null references in the array.
3. **null**: The third test case is similar to the previous one, but instead of assigning `undefined`, it assigns `null` to each array element (`payload[i]`).

**Options Compared:**

The benchmark compares three different approaches:

*   Deleting an element from the array (`delete`)
*   Assigning `undefined` to an element in the array (creating null references)
*   Assigning `null` to an element in the array

**Pros and Cons of Each Approach:**

1.  **Deleting an Element:** This approach is straightforward and can be more efficient since it doesn't create unnecessary references in the array. However, it might have performance implications if the array is large or if the delete operation itself takes significant time.
2.  **Assigning `undefined` to an Element:** Creating null references in the array can lead to memory leaks if not handled properly. However, this approach can be more efficient than deleting elements since it doesn't involve any complex operations like delete.
3.  **Assigning `null` to an Element:** Similar to assigning `undefined`, this approach creates references in the array but might have different performance implications depending on how null checks are performed in the JavaScript engine.

**Special JS Features or Syntax:**

The test case uses a special syntax called "short variable declaration" which was introduced in ECMAScript 2015 (ES6). This syntax allows declaring variables without using the `var`, `let`, or `const` keywords, making the code more concise and expressive. The syntax used here is `for (let i = 1000; i--;)`.

**Library Usage:**

There is no library usage in these test cases.

**Other Considerations:**

*   The benchmark assumes that the JavaScript engine can handle the array resizing or shifting operations efficiently, which might not always be the case.
*   The `Script Preparation Code` initializes the array and populates it with values before running each individual test case. This ensures a consistent state for the benchmark.

**Alternatives:**

Some alternative approaches to compare in this benchmark could include:

*   Assigning values to an empty array using `push()` or `unshift()`
*   Using `splice()` to remove elements from the end of the array
*   Creating and destroying temporary arrays
*   Using different data structures, such as linked lists or sets

However, these alternatives might not be relevant for this specific benchmark, which focuses on comparing deletion, assignment of `undefined`, and assignment of `null` in an array.

Related benchmarks:

JS delete vs undefined vs null (version: 0)

Comparing performance of: delete vs undefined vs null

Created: 2 years ago by: Guest

Jump to the latest result

delete

undefined

null

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):