Benchmark: forEach vs reduce on nested values

Script Preparation code:

var arr = [{
    item: {
        id: 1,
        name: "Abc"
    },
    amount: 1
}, {
    item: {
        id: 1,
        name: "Abc"
    },
    amount: 2
}, {
    item: {
        id: 2,
        name: "Abc"
    },
    amount: 2
},{
    item: {
        id: 1,
        name: "Abc"
    },
    amount: 2
}];

Tests:

forEach
let merged = {} arr.forEach( element => { if (merged[element.item.id]) { merged[element.item.id].amount += element.amount } else { merged[element.item.id] = element } })
Reduce
Object.values(arr.reduce((a,curr)=>{ if(!a[curr.item.id]) a[curr.item.id] = curr; else a[curr.item.id].amount += curr.amount; return a; },{}));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
Reduce

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.67 Safari/537.36

Browser/OS: Chrome 70 on Windows

View result in a separate tab

Test name	Executions per second
forEach	2666942.2 Ops/sec
Reduce	1441377.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the provided JSON and explain what is being tested, compared, and discussed.

**Benchmark Definition**

The benchmark is designed to compare the performance of two different approaches: using `Array.prototype.forEach` versus using `Array.prototype.reduce`. The test case creates an array of objects with nested properties (`item.id` and `amount`) and then uses these functions to merge and calculate the total amount for each unique `id`.

**Options Compared**

The two options being compared are:

1. **Using `Array.prototype.forEach`**: This approach iterates over the array using a callback function, which is executed once for each element in the array.
2. **Using `Array.prototype.reduce`**: This approach uses a reducer function to accumulate values as it iterates over the array.

**Pros and Cons**

* **forEach**:
	+ Pros: Easy to read and write, intuitive syntax.
	+ Cons: Can be slower than `reduce`, especially for large arrays, due to the overhead of function calls.
* **Reduce**:
	+ Pros: Optimized for performance, can handle large arrays more efficiently, since it uses a single accumulator value.
	+ Cons: More complex syntax, might require more memory to store the accumulator.

In general, `reduce` is a good choice when:

* You need to accumulate values from an array.
* You're working with large datasets.
* Performance is critical.

On the other hand, `forEach` is a better choice when:

* You need to perform side effects (e.g., updating DOM elements).
* Your code needs to be easy to read and write.
* You don't care about performance.

**Library**

There are no libraries used in this benchmark definition. However, it's worth noting that some browsers might have optimized implementations of these functions that could affect the results.

**Special JS Feature or Syntax**

None mentioned in this specific benchmark definition.

**Other Considerations**

When writing performance-critical code, consider the following:

* Use `const` and `let` instead of `var` to reduce variable scope.
* Avoid using unnecessary function calls or loops.
* Use caching mechanisms when possible (e.g., memoization).
* Optimize for cache coherency and parallel execution.

**Alternatives**

If you're looking for alternative approaches, consider:

* Using a library like Lodash, which provides optimized implementations of common functions, including `forEach` and `reduce`.
* Implementing custom optimizations using JavaScript's built-in features (e.g., `map`, `filter`) or by using specialized libraries.
* Profiling your code to identify performance bottlenecks and optimizing those areas specifically.

Keep in mind that the best approach depends on the specific use case, data structure, and performance requirements.

Related benchmarks:

forEach vs reduce on nested values (version: 0)

Comparing performance of: forEach vs Reduce

Created: 6 years ago by: Guest

Jump to the latest result

forEach

Reduce

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):