Benchmark: array push vs reduce

Script Preparation code:

var oldData = { item1: 'olditem1', item2: 'olditem2', item3: 'unchanged' };
var newData = { item1: 'newitem1', item3: 'unchanged', item4: 'something else' };

Tests:

array push
const result = []; Object.entries(oldData).forEach(([key, oldValue]) => { const newValue = newData[key]; if (typeof newValue === 'undefined' || oldValue !== newValue) { result.push(key); } });
optimized push
const result = []; Object.keys(oldData).forEach((key) => { if (oldData[key] !== newData[key]) { result.push(key); } });
reduce
const result = Object.entries(oldData).reduce((accum, [key, oldValue]) => { const newValue = newData[key]; if (typeof newValue === 'undefined' || oldValue !== newValue) { return [...accum, key]; } return accum; }, []);
optimized reduce
const result = Object.keys(oldData).reduce((accum, key) => { if (oldData[key] !== newData[key]) { accum.push(key); } return accum; }, []);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array push
optimized push
reduce
optimized reduce

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:137.0) Gecko/20100101 Firefox/137.0

Browser/OS: Firefox 137 on Windows

View result in a separate tab

Test name	Executions per second
array push	8867529.0 Ops/sec
optimized push	12721282.0 Ops/sec
reduce	8143050.5 Ops/sec
optimized reduce	12808278.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Measuring performance differences between various approaches to achieve the same result is crucial in understanding how different coding techniques impact execution speed.

The provided benchmark compares three methods for detecting and updating items that have changed:

1.  **Array Push Method**

*   This approach iterates through an object's entries (key-value pairs) using `Object.entries()`. For each entry, it checks if the corresponding value in a new object (`newData`) is different from the original value in the old data object (`oldData`). If they are different, the key is added to an array.
    *   **Pros:**

*   This approach is straightforward and easy to understand for those familiar with JavaScript objects.
        *   It does not require any special libraries or features.
    *   **Cons:**

*   It has a time complexity of O(n), where n is the number of key-value pairs in the object. However, in practice, this may be slower than other approaches because it requires creating an array and pushing elements to it for each iteration.
    *   **Other Considerations:**

*   This approach can be optimized further by using `for...in` loop instead of `Object.entries()` or by using a library like Lodash's `differenceBy` method.

2.  **Optimized Push Method**

*   Similar to the array push method, this approach uses `Object.keys()` and `forEach()` to iterate through an object's keys (strings representing the key names). For each key, it checks if the corresponding value in `newData` is different from `oldData[key]`. If they are different, the key is added to an array.
    *   **Pros:**

*   This approach also has a time complexity of O(n), similar to the array push method. However, it avoids creating an array and pushing elements, which can be more efficient in practice.
    *   **Cons:**

*   This approach may not be as straightforward or intuitive for those unfamiliar with `Object.keys()` and `forEach()`.
        *   It uses a few more operations compared to the array push method.
3.  **Reduce Method**

*   This approach uses `Array.prototype.reduce()` to combine an accumulator with each key-value pair in the object. For each iteration, it checks if the corresponding value in `newData` is different from `oldData[key]`. If they are different, the key is added to the accumulator array.
    *   **Pros:**

*   This approach can be more efficient than array push methods because it avoids creating and pushing arrays. However, it also uses more operations and may require a good understanding of how `Array.prototype.reduce()` works.

*   **Cons:**

*   This approach has a steeper learning curve due to the use of `reduce()`. It might be difficult for developers without prior experience with this method.
        *   The time complexity is also O(n) because it requires iterating through all key-value pairs in the object. However, the overhead of calling `Array.prototype.reduce()` may lead to slower performance in practice compared to other methods.
4.  **Optimized Reduce Method**

*   Similar to the reduce method, this approach uses `Object.keys()` and `reduce()` but avoids creating an initial array by using the spread operator (`...`) to initialize the accumulator array with `[]` when called for the first time.

*   This approach has a similar trade-off between readability and performance as the optimized push method.
    *   **Pros:**

*   Optimized reduce is more efficient because it avoids creating an additional array when calling `reduce()`.
    *   **Cons:**

*   The use of spread operator might be unfamiliar to developers without prior experience with advanced JavaScript syntax.

Related benchmarks:

array push vs reduce (version: 0)

Comparing performance of: array push vs optimized push vs reduce vs optimized reduce

Created: 2 years ago by: Guest

Jump to the latest result

array push

optimized push

reduce

optimized reduce

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):