Benchmark: Add item to array: push vs assign

Script Preparation code:

window.MAX_SIZE = 1000;

Tests:

Push item to an array
const items = []; for (let i = 0; i < MAX_SIZE; ++i) { items.push(i); }
Direct assign an item to an array
const items = []; for (let i = 0; i < MAX_SIZE; ++i) { items[i] = i; }
Direct assign an item to an initialized array
const items = new Array(MAX_SIZE); for (let i = 0; i < MAX_SIZE; ++i) { items[i] = i; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Push item to an array
Direct assign an item to an array
Direct assign an item to an initialized array

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its components.

**Benchmark Definition JSON**

The benchmark definition is a JSON object that provides metadata about the test. In this case, it defines three individual test cases:

* `Name`: A unique name for the benchmark.
* `Description`: An optional description of the benchmark (not provided in this example).
* `Script Preparation Code` and `Html Preparation Code`: These are code snippets that are executed before running the actual test.

In this case, only the `Script Preparation Code` is provided, which sets a constant `MAX_SIZE` to 1000. This suggests that the tests will be comparing the performance of adding an item to an array using different methods (push vs direct assignment) on an array with a fixed size of 1000.

**Individual Test Cases**

Each test case has two components:

* `Benchmark Definition`: A JavaScript code snippet that defines the test scenario.
* `Test Name`: A descriptive name for the test case.

There are three test cases, each testing a different method for adding an item to an array:

1. **Push item to an array**: This test uses a simple loop to push items onto an empty array using the `push` method.
2. **Direct assign an item to an array**: This test directly assigns values to existing elements in the array, rather than creating new elements using `push`.
3. **Direct assign an item to an initialized array**: This test creates an initialized array with a fixed length and then assigns values to its elements.

**Library Used**

The benchmark uses the built-in JavaScript `Array` object and its methods (e.g., `push`, indexing).

**Special JS Features or Syntax**

None are explicitly mentioned in the provided code snippets. However, some older browsers might have quirks when it comes to array literals, especially with respect to their parsing behavior.

**Options Compared**

The benchmark is comparing three different approaches for adding an item to an array:

* **Push**: Using `push` method to add new elements to the end of the array.
* **Direct Assign**: Directly assigning values to existing elements in the array.
* **Direct Assign (Initialized Array)**: Creating an initialized array with a fixed length and then assigning values to its elements.

**Pros and Cons**

Here's a brief overview of each approach:

1. **Push**:
	* Pros: Efficient, flexible, and widely supported.
	* Cons: May create multiple garbage collections due to the creation of new arrays.
2. **Direct Assign**:
	* Pros: Can be faster for large datasets since it avoids creating new arrays.
	* Cons: Limited to assigning values to existing elements; inefficient for adding new elements.
3. **Direct Assign (Initialized Array)**:
	* Pros: Provides a good balance between efficiency and flexibility.
	* Cons: Requires careful management of the array's length, as it can lead to memory allocation issues.

**Other Alternatives**

Some alternative approaches that could be considered in similar benchmarks:

1. **Using `Array.prototype.splice()`**: Instead of creating new arrays or using `push`, some tests might use `splice` to add elements at specific indices.
2. **Comparing array performance with modern JavaScript features**: Some benchmark might also compare the performance of different modern JavaScript features, such as using `at()` or `findIndex()` for array access and manipulation.

Overall, this benchmark provides a straightforward comparison of three common approaches for adding items to an array in JavaScript, which can be useful for identifying potential performance bottlenecks in web applications.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/115.0

Browser/OS: Firefox 115 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Push item to an array	192190.2 Ops/sec
Direct assign an item to an array	173643.4 Ops/sec
Direct assign an item to an initialized array	218993.4 Ops/sec

Related benchmarks:

Add item to array: push vs assign (version: 0)

Comparing performance of: Push item to an array vs Direct assign an item to an array vs Direct assign an item to an initialized array

Created: one year ago by: Guest

Jump to the latest result

Push item to an array

Direct assign an item to an array

Direct assign an item to an initialized array

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):