Benchmark: Array.reduce vs for loop vs Array.forEach vs decrement while 3

Script Preparation code:

// Create an array of 1000 random intergers between 1 and 10000
var arrRandom = [];
for(var intCtr=0; intCtr<1000; intCtr++) {
  arrRandom.push(Math.floor(Math.random() * Math.floor(10000)));
}

function reduceCallback(accum, curr, index) {
	accum[curr] = index;
  	return accum;
}

function doRedeuce(pArray) {
	return pArray.reduce(reduceCallback, {});
}
function doLoop(pArray) {
	var accum = {};
	for(var index=0; index<pArray.length; index++) {
		accum[pArray[index]] = index;
	}
	return accum;
}
function decrWhile(pArray) {
	var accum = {};
  	var index = pArray.length;
	while(index--) {
		accum[pArray[index]] = index;
	}
	return accum;
}
function doForEach(pArray) {
	var accum = {};
	pArray.forEach(function(item, index) {
		accum[item] = index;
	});
  return accum;
}

Tests:

reduce
var redeuceResult = doRedeuce(arrRandom);
for loop
var loopResult = doLoop(arrRandom);
forEach
var forEachResult = doForEach(arrRandom);
decrement while
var decrWhileResult=0; decrWhileResult = decrWhile(arrRandom);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce
for loop
forEach
decrement while

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared options, pros and cons of those approaches, library usage, special JavaScript features or syntax, and other considerations.

**Benchmark Definition**

The benchmark measures the performance of four different methods to sum an array of 1000 random integers between 1 and 10,000:

1. `Array.reduce()`
2. A traditional "for loop" (also known as a `for`-style loop)
3. `Array.forEach()`
4. A decrementing while loop (`while` loop with decreasing index)

**Comparison Options**

The four methods are compared in terms of their performance, measured by the number of executions per second.

**Pros and Cons of Each Approach:**

1. **Array.reduce()**: This method is often considered one of the most concise and expressive ways to perform array transformations. However, it can be slower than traditional loops due to the overhead of function calls and object lookups.
	* Pros: Concise code, easy to read
	* Cons: Can be slower, may incur overhead for large arrays
2. **Traditional For Loop**: This method is a straightforward, classic approach that has been used for decades. It can be faster than `Array.reduce()` but requires more lines of code.
	* Pros: Fast, well-known algorithm
	* Cons: More verbose code, may not be as concise or expressive
3. **Array.forEach()**: Similar to `Array.reduce()`, `forEach()` is designed for array iterations, but it doesn't accumulate the results like `reduce()`. It's often used when you need to perform an action on each element without modifying the original array.
	* Pros: Fast, easy to use
	* Cons: Doesn't accumulate results, may not be suitable for all use cases
4. **Decrementing While Loop**: This method is a more traditional approach that uses a decreasing index to iterate through the array. It can be faster than `Array.reduce()` and `Array.forEach()`, but requires more manual bookkeeping.
	* Pros: Fast, flexible indexing control
	* Cons: More verbose code, may require manual indexing

**Library Usage**

None of the methods use external libraries. However, it's worth noting that `Array.prototype.reduce()` is a built-in method in JavaScript.

**Special JavaScript Features or Syntax**

None of the benchmarked methods explicitly utilize special JavaScript features like `let` or `const` for variable declarations, arrow functions, or template literals (although some of these features might be used implicitly in the surrounding code).

**Other Considerations**

* The benchmark assumes that the input array is already populated with random integers. If the data was generated on-the-fly during measurement, it could introduce additional variability.
* The `for`-style loop uses a traditional indexing approach (i.e., `index = pArray.length - 1`). A more modern approach might use a more efficient indexing method or even a library like Lodash's `range()` function.

**Alternatives**

Other methods that could be used to sum an array of numbers include:

* Using the `every()` and `some()` methods in combination (e.g., checking if all elements are above a certain threshold)
* Utilizing `Math.min()` and `Math.max()` with multiple calls to reduce or iterate over the array
* Implementing a custom solution using bitwise operations, such as using `Math.pow(2, 15)` for shifting bits

Keep in mind that these alternatives might not be suitable for all use cases or performance-critical code.

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36

Browser/OS: Chrome 74 on Windows

View result in a separate tab

Test name	Executions per second
reduce	1761.5 Ops/sec
for loop	1520.3 Ops/sec
forEach	1867.2 Ops/sec
decrement while	2142.6 Ops/sec

Related benchmarks:

Array.reduce vs for loop vs Array.forEach vs decrement while 3 (version: 0)

A test summing 1000 random numbers, 1 - 10000

Comparing performance of: reduce vs for loop vs forEach vs decrement while

Created: 5 years ago by: Guest

Jump to the latest result

reduce

for loop

forEach

decrement while

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):