Benchmark: Array Push vs. Index Access

Script Preparation code:

var array = [1, 2, 3, 4];

Tests:

Array.prototype.push
array.push(5);
Access Index
array[array.length] = 5;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.push
Access Index

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36

Browser/OS: Chrome 87 on Windows

View result in a separate tab

Test name	Executions per second
Array.prototype.push	7100757.5 Ops/sec
Access Index	3980926.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmarking test case on the MeasureThat.net website. The benchmark tests the performance of two approaches:

1.  **Array.prototype.push**: This method adds one or more elements to the end of an array and returns the new length of the array.
2.  **Access Index**: This approach accesses the last element of the array directly using the index `array[array.length]` and assigns a new value to it.

**Options Compared**

The benchmark compares the performance of these two approaches:

*   **Array.prototype.push**: The method that adds an element to the end of the array.
*   **Access Index**: The approach that accesses the last element of the array directly and modifies it.

**Pros and Cons of Each Approach**

### Array.prototype.push

Pros:

*   **Memory Management**: This approach avoids modifying the original array's indices, which can be beneficial when working with large datasets.
*   **Code Readability**: Using `Array.prototype.push` is a common and idiomatic JavaScript pattern, making the code more readable.

Cons:

*   **Performance Overhead**: The `push` method creates a new array object, copies the old elements to it, and then updates the length of the original array. This can be slower than accessing an element directly.
*   **Memory Allocation**: Creating a new array object requires allocating memory, which can lead to performance issues if the array is very large.

### Access Index

Pros:

*   **Direct Access**: This approach allows direct access to the last element of the array without creating a new array or modifying indices.
*   **Performance**: Directly accessing an element can be faster than using `Array.prototype.push` because it avoids the overhead of creating a new array object.

Cons:

*   **Code Complexity**: Using the index-based approach makes the code less readable and more prone to errors, as it requires careful handling of array indices.
*   **Index Bounds Checking**: This approach assumes that the last element exists; if the array is empty, accessing an out-of-bounds index can lead to runtime errors.

**Library Usage**

There is no explicit library mentioned in the provided JSON. However, some libraries like Lodash or Array.prototype methods might be used in real-world scenarios for similar operations.

**Special JavaScript Features/Syntax**

This benchmark does not explicitly use any special JavaScript features or syntax. It only tests basic array operations.

**Alternative Approaches**

If you need to optimize array push performance, consider the following alternatives:

*   **Using `Array.prototype.splice()`**: Instead of using `push()`, you can use `splice()` with an offset of 0 and a count of 1 to add an element to the end of the array.
*   **Using a Typed Array**: If you're working with large datasets, consider using typed arrays like `Int32Array` or `Float64Array` for more efficient memory allocation.
*   **Using Native WebAssembly (WASM)**: For even better performance, you can use WASM and its optimized array operations.

Keep in mind that the best approach depends on your specific use case and requirements. Always consider factors like code readability, maintainability, and performance when choosing an optimization technique.

Related benchmarks:

Array Push vs. Index Access (version: 0)

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

Created: 3 years ago by: Registered User

Jump to the latest result

Array.prototype.push

Access Index

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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