Benchmark: push vs. Index write performance

Script Preparation code:

var arr = [1, 1, 1, 1, 1];

Tests:

Array.prototype.push
arr.push(1);
Index write
arr[arr.length] = 1;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.push
Index write

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.2:3b, generated 5 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested.

**Benchmark Definition**

The benchmark definition is represented by two JSON objects, each containing a `Benchmark Definition` property that specifies the JavaScript code to be executed. In this case, we have two test cases:

1. `Array.prototype.push`: This test case executes the line of code `arr.push(1);`, which attempts to add an element to the end of the array.
2. `Index write`: This test case executes the line of code `arr[arr.length] = 1;`, which directly assigns a value to the last index of the array.

**Options Compared**

These two test cases compare the performance of two approaches:

* **Push method**: The `push` method adds an element to the end of the array, shifting all existing elements one position forward. This can lead to efficient allocation and deallocation of memory.
* **Index write method**: The `arr[arr.length] = 1;` syntax directly assigns a value to the last index of the array. While this may seem more straightforward, it can lead to inefficiencies due to the overhead of accessing and modifying individual elements.

**Pros and Cons**

**Push Method:**

Pros:

* Efficient allocation and deallocation of memory
* Can handle arrays with large numbers of elements without significant performance impact

Cons:

* May be slower for small arrays or when adding a single element
* Requires an extra operation to update the length property of the array

**Index Write Method:**

Pros:

* Faster execution time, especially for small arrays or when adding a single element
* Does not require updating the length property of the array

Cons:

* Can lead to inefficiencies due to the overhead of accessing and modifying individual elements
* May cause memory fragmentation if the array is large

**Library and Purpose**

In both test cases, the `arr` variable is an instance of the built-in JavaScript Array object. The `Array.prototype.push` method is a standard method of the Array prototype chain, providing a convenient way to add elements to the end of the array.

The `index write` method, on the other hand, is not a standardized method of the Array prototype chain. It is a common idiom used in some JavaScript implementations to assign a value to the last index of an array. However, this syntax is not supported by all JavaScript engines or environments.

**Other Alternatives**

There are alternative approaches to comparing the performance of these two methods:

* **Use a larger array**: Experimenting with larger arrays can help illustrate the difference in performance between the `push` method and the `index write` method.
* **Add multiple elements**: Increasing the number of elements added using the `push` method or the `index write` method can provide more insight into their relative performance.
* **Use a different data structure**: Comparing the performance of these two methods on different data structures, such as linked lists or sparse arrays, can provide additional context.

**Special JS Feature**

There is no special JavaScript feature mentioned in this benchmark definition. However, if we were to explore other benchmarks that involve special features like `for...of` loops, arrow functions, or generators, we would need to consider the specific requirements and constraints of each test case.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_1_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.146 Safari/537.36

Browser/OS: Chrome 88 on Mac OS X 11.1.0

View result in a separate tab

Test name	Executions per second
Array.prototype.push	12645370.0 Ops/sec
Index write	7468793.0 Ops/sec

Related benchmarks:

push vs. Index write performance (version: 0)

Comparing performance of: Array.prototype.push vs Index write

Created: 3 years ago by: Guest

Jump to the latest result

Array.prototype.push

Index write

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.2:3b, generated 5 days ago):