Benchmark: forEach vs manual

Script Preparation code:

let items = [];

for (let i = 0; i < 100; i++) {
	items.push({
		something: i
	});
}
window.items = items;

Tests:

forEach
let items = window.items; let theThing; items.forEach(i => { let item = i.something; if (theThing || i === 3) { theThing = i + 3; } }); return theThing;
Cache len
let items = window.items; let theThing; let len = items.length; for (let i = 0; i < len; i++) { let item = items[i].something; if (theThing || item === 3) { theThing = item + 3; } } return theThing;
No cache len
let items = window.items; let theThing; for (let i = 0; i < items.length; i++) { let item = items[i]; if (theThing || item === 3) { theThing = item + 3; } } return theThing;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
Cache len
No cache len

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided benchmark measures the performance of three different approaches for a specific task: iterating over an array to find and update a value.

**Task Description**

The task is to iterate over an array of objects, where each object has a "something" property. The goal is to find the first occurrence of a certain condition (in this case, `item === 3`) and update a variable (`theThing`) with the result of adding 3 to the matched value.

**Approach Comparison**

There are three approaches compared in this benchmark:

1. **`forEach`**: Uses the `forEach` method to iterate over the array. This approach is often preferred for its concise syntax and ease of use.
2. **Cache `len`**: Caches the length of the array before the loop, reducing the number of iterations required to access the array's length property.
3. **No cache `len`**: Does not cache the array length, requiring repeated lookups during iteration.

**Pros and Cons**

1. **`forEach`**:
	* Pros: Concise syntax, easy to read and write, and often considered a more modern and efficient approach.
	* Cons: May be slower due to overhead of function calls and object inspection.
2. **Cache `len`**:
	* Pros: Can reduce iteration overhead by caching the array length.
	* Cons: May not improve performance if the array is large or has many elements, as cache misses can occur during iteration.
3. **No cache `len`**:
	* Pros: No additional memory allocation or caching required, potentially reducing memory pressure.
	* Cons: More verbose syntax and may be slower due to repeated lookups of array length.

**Library Usage**

The benchmark uses the `window.items` property as an example array, suggesting that it is a global variable or a DOM element containing the data. The `forEach` method is also used, which implies that the browser supports ECMAScript 5 (ES5) or later versions of JavaScript.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark, such as async/await, Promises, or other advanced constructs.

**Other Alternatives**

Other approaches to iterating over an array and updating a value might include:

* Using `for` loops with explicit indexing (`i = 0; i < arr.length; i++`)
* Utilizing modern JavaScript features like `map()`, `filter()`, and `reduce()` for more functional programming-inspired solutions
* Leveraging libraries or frameworks that provide optimized array iteration and caching mechanisms

Related benchmarks:

forEach vs manual (version: 0)

Comparing performance of: forEach vs Cache len vs No cache len

Created: 9 years ago by: Guest

Jump to the latest result

forEach

Cache len

No cache len

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):