Benchmark: Array: delete vs undefined

Script Preparation code:

var arr1 = [];
var arr2 = [];
for(let i = 0; i < 100000; i++) {
  arr1[i] = i;
  arr2[i] = i;
}

Tests:

Delete array element
for(let i = 0; i < 100000; i++) { delete arr1[i]; }
Set array element to undefined
for(let i = 0; i < 100000; i++) { arr2[i] = undefined; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Delete array element
Set array element to undefined

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 explanation of the benchmark provided by MeasureThat.net.

**Benchmark Definition**

The benchmark measures the performance difference between two approaches:

1.  **Deleting an element from an array**: The first test case, "Delete array element", uses the `delete` keyword to remove an element from the `arr1` array. This approach checks how efficient JavaScript is when deleting elements from an array.
2.  **Setting an element to undefined**: The second test case, "Set array element to undefined", sets each element in the `arr2` array to `undefined`. This approach tests how efficient JavaScript is when setting an element to a specific value.

**Options Compared**

The benchmark compares two approaches:

*   **Deleting an element from an array (`delete` keyword)**: This approach uses the `delete` keyword to remove an element from the array. It's a way to explicitly mark an element as deleted, but it can be slower than other methods.
*   **Setting an element to undefined**: This approach sets each element in the array to `undefined`, which is the default value for elements when they're not set explicitly.

**Pros and Cons**

Here are some pros and cons of each approach:

*   **Deleting an element from an array (`delete` keyword)**:
    *   Pros: This approach can be useful if you need to remove elements from an array, as it marks the element as deleted.
    *   Cons: It's generally slower than setting an element to `undefined`, especially for large arrays.
*   **Setting an element to undefined**:
    *   Pros: This approach is faster than deleting an element, especially for large arrays. It also sets all subsequent elements to `undefined`.
    *   Cons: If you don't need the value of the original element, using `undefined` might not be the most efficient choice.

**Library and Special JS Feature**

There's no library used in this benchmark, but there is a special feature being tested: **JavaScript engines' behavior when deleting or setting elements to undefined**. The benchmark measures how JavaScript engines handle these operations, which can affect performance.

**Other Considerations**

When dealing with large arrays, using `undefined` instead of deleting an element might be a better choice if you don't need the value of the original element. However, if you need to remove elements from an array, using the `delete` keyword is still a good option.

Keep in mind that these benchmarks are usually run on specific JavaScript engines (e.g., V8 for Chrome), and results may vary depending on the engine and other factors like hardware and system configuration.

**Other Alternatives**

If you're interested in benchmarking different approaches to removing elements from an array or setting elements to `undefined`, MeasureThat.net provides various benchmarks. For example, you can also compare:

*   Using `splice()` instead of `delete`
*   Using a loop with a variable index instead of `delete` or `splice()`
*   Using a library like Lodash's `omit()` function

These alternatives might provide more insight into the performance differences between various approaches.

Related benchmarks:

Array: delete vs undefined (version: 0)

Comparing performance of: Delete array element vs Set array element to undefined

Created: 3 years ago by: Registered User

Jump to the latest result

Delete array element

Set array element to undefined

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):