Benchmark: Array loop vs foreach vs map vs for...in

Script Preparation code:

   var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = i;
    }
  
    function someFn(i) {
      return i * 3 * 8;
    }

Tests:

foreach
arr.forEach(function (item){ someFn(item); })
for
for (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
map
arr.map(item => someFn(item))
for...of
for (const i of arr) { someFn(i) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
map
for...of

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:97.0) Gecko/20100101 Firefox/97.0

Browser/OS: Firefox 97 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
foreach	94162.1 Ops/sec
for	586828.2 Ops/sec
map	54128.6 Ops/sec
for...of	101910.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested, compared, and analyzed.

**Benchmark Definition**

The benchmark defines four different approaches to iterate over an array of 1000 elements and apply a function `someFn` to each element:

1. **Array loop**: A traditional for loop using the index `i` to access each element.
2. **foreach**: Using the `forEach()` method, which calls the provided callback function for each element in the array.
3. **map**: Using the `map()` method, which returns a new array with the results of applying the provided callback function to each element.
4. **for...of**: Using the new `for...of` loop syntax, which iterates over the elements of an array without using indices.

**Test Cases**

The benchmark includes four individual test cases, each representing one of the above approaches:

1. **foreach**: Iterates over the array using the `forEach()` method.
2. **for**: Uses a traditional for loop with the index `i` to access each element.
3. **map**: Applies the `someFn` function to each element using the `map()` method, returning a new array with the results.
4. **for...of**: Iterates over the array using the new `for...of` loop syntax.

**Comparison and Analysis**

The benchmark compares the execution performance of each approach on the same test case, which is likely optimized for each iteration method. The comparison highlights the differences in performance between the various approaches:

* **Array loop**: The traditional for loop seems to be the slowest.
* **foreach**: Using `forEach()` provides a decent balance between performance and readability.
* **map**: Applying the function using `map()` returns a new array, which might incur additional overhead. However, it's still relatively fast compared to the array loop.
* **for...of**: The new `for...of` loop syntax is surprisingly efficient, making it a viable alternative to traditional for loops.

**Library and Special JS Features**

None of the test cases explicitly use any external libraries or special JavaScript features beyond the standard ECMAScript syntax. However, the `map()` method does rely on the Array prototype's `map()` function, which might be specific to certain browsers or implementations.

**Pros and Cons**

Here's a summary of the pros and cons for each approach:

* **Array loop**: Slowest, but most control over iteration.
	+ Pros: Flexibility and understanding the underlying mechanics.
	+ Cons: Error-prone and verbose.
* **foreach**: Balances performance and readability.
	+ Pros: Easy to understand and use, decent performance.
	+ Cons: May incur additional overhead compared to native methods like `map()` or `for...of`.
* **map**: Returns a new array with results, incurs some overhead.
	+ Pros: Simplifies code, provides a readable way to transform data.
	+ Cons: May not be the fastest option due to the returned value and potential additional processing.
* **for...of**: Efficient and modern syntax.
	+ Pros: Fast, easy to read and write, and future-proof.
	+ Cons: Less control over iteration compared to traditional for loops.

**Other Alternatives**

Some other alternatives to consider when iterating over arrays in JavaScript:

* **filter()`, `every()`, or `some()` methods**: Useful for filtering or testing individual elements in the array.
* **reduce()` method**: Applies a function to each element, accumulating a result.
* **iterators` and ` generators`: More advanced topics for working with iterable objects.

In conclusion, the benchmark provides valuable insights into the performance differences between various iteration approaches in JavaScript. The choice of method depends on trade-offs between performance, readability, and control over iteration.

Related benchmarks:

Array loop vs foreach vs map vs for...in (version: 0)

Comparing performance of: foreach vs for vs map vs for...of

Created: 2 years ago by: Guest

Jump to the latest result

foreach

for

map

for...of

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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