Benchmark: One million ForEach vs Concat

Tests:

ForEach
var selected = []; var unselected = []; for (var i = 0; i < 1000000; i++) { selected.push(i+'selected') } for (var j = 0; j < 1000000; j++) { unselected.push(i+'unselected') } unselected.forEach((item) => { selected.push(item) });
Concat
var selected = []; var unselected = []; for (var i = 0; i < 1000000; i++) { selected.push(i+'selected') } for (var j = 0; j < 1000000; j++) { unselected.push(i+'unselected') } var concat = selected.concat(unselected);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
ForEach
Concat

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark measures the performance difference between two approaches for pushing elements to an array: using `forEach` (or equivalent) and concatenating arrays (`concat`). Both test cases create two large arrays, `selected` and `unselected`, by iterating over a million iterations. The first loop populates each array with strings in the format "numberselected" or "numberunselected". The second loop copies elements from one array to another using either `forEach` or concatenation.

**Options Compared**

The two options being compared are:

1. **ForEach (or equivalent)**: This approach uses the `forEach` method, which executes a callback function once for each element in an iterable (like an array). It's often considered more readable and maintainable than concatenating arrays.
2. **Concatenation**: This approach uses the `concat` method to merge two or more arrays into one.

**Pros and Cons**

*   **ForEach**:
    *   Pros:
        *   More readable and maintainable code.
        *   Can be more efficient since it avoids creating a new array.
    *   Cons:
        *   May incur additional overhead due to the callback function execution.
        *   Can be slower if the callback is complex or has side effects.
*   **Concatenation**:
    *   Pros:
        *   Simple and easy to understand.
        *   Often faster since it avoids callback function overhead.
    *   Cons:
        *   Creates a new array, which can be memory-intensive for large datasets.
        *   May lead to slower performance due to the intermediate array creation.

**Library: Lodash**

The `forEach` method used in the benchmark is part of the Lodash library. Lodash is a popular JavaScript utility library that provides various functional programming helpers, including iteration and mapping functions like `forEach`. It's often used for simplicity and readability, but can add unnecessary overhead due to its callback function execution.

**Special JS Feature/Syntax**

The benchmark does not use any special JavaScript features or syntax. However, it's worth noting that the `let` keyword is used instead of `var`, which is a more modern and recommended way to declare variables in JavaScript.

**Alternatives**

For this specific benchmark, some alternatives could be:

*   **Using an array reducer**: Instead of concatenating arrays, you could use an array reducer function (e.g., `Array.prototype.reduce`) to accumulate elements into the resulting array.
*   **Using a streaming approach**: If the dataset is too large for in-memory computation, consider using a streaming approach that processes elements one by one without loading the entire dataset into memory.

Keep in mind that these alternatives might not be as straightforward or readable as the original code and would likely require more significant changes to the benchmark setup.

Related benchmarks:

One million ForEach vs Concat (version: 0)

Comparing performance of: ForEach vs Concat

Created: 4 years ago by: Registered User

Jump to the latest result

ForEach

Concat

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):