Benchmark: Array loop vs foreach vs map noFx_1k

Script Preparation code:

var arr = [];
for (let i = 0; i < 1000; i++) {
    arr[i] = i;
}
var len = arr.length

Tests:

foreach
arr.forEach(item => item);
for
for (let i = 0; i < len; i++) { return arr[i]; }
map
arr.map(item => item);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for
map

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36

Browser/OS: Chrome 85 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
foreach	3002945.0 Ops/sec
for	8065733.0 Ops/sec
map	421831.2 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the provided benchmark.

**What is tested on the provided JSON?**

The provided JSON represents three microbenchmarks that test the performance of JavaScript loops: `foreach`, `for`, and `map`. The benchmarks are designed to measure which loop construct is fastest for performing a simple array operation. Specifically, each benchmark creates an empty array, populates it with numbers from 0 to 999 using a loop, and then measures the time taken to execute the loop.

**Options compared**

The three options being compared are:

1. `foreach` (`.forEach()` method)
2. `for` (traditional loop syntax)
3. `map` (`.map()` method)

These options represent different approaches to iterating over an array in JavaScript.

**Pros and cons of each approach:**

*   **foreach**: The `.forEach()` method is a concise way to iterate over an array, but it's often slower than traditional loops because of the overhead of calling the callback function for each element. It also has performance implications when dealing with large arrays or complex operations.
*   **for**: Traditional loop syntax is generally faster and more efficient, especially when working with large datasets. However, it can be verbose and prone to errors if not implemented correctly. Additionally, modern JavaScript engines often optimize traditional loops better than `.forEach()` method calls.
*   **map**: The `.map()` method is another concise way to iterate over an array, but it's often slower than traditional loops because of the overhead of creating a new array and calling the callback function for each element. It also has performance implications when dealing with large arrays or complex operations.

**Other considerations:**

*   **Array length**: The benchmark creates an empty array with 1000 elements to ensure that the loop has to iterate over a non-trivial dataset.
*   **JavaScript engine**: The test is run on Chrome 85, which may have optimized its execution of loops compared to other JavaScript engines.

**Library and special JS features:**

None of the provided benchmarks rely on any external libraries. However, they do utilize some standard JavaScript features:

*   `let` and `const`: The benchmark uses `let` and `const` for variable declarations to ensure that the variables are not hoisted.
*   Arrow functions (`=>`): Two of the benchmarks use arrow functions (`.forEach()` and `.map()`) which can be useful when writing concise code.

**Alternative approaches:**

There are other loop constructs available in JavaScript, such as:

*   `while`: A traditional loop construct that uses a conditional statement to control the iteration.
*   `for...in`: A loop construct that iterates over an object's property names.
*   `reduce()`: A method that reduces an array of values into a single output value.

These alternative approaches may have their own performance implications and use cases, and are not directly comparable to the `.forEach()` and traditional loops.

Related benchmarks:

Array loop vs foreach vs map noFx_1k (version: 0)

Comparing performance of: foreach vs for vs map

Created: 4 years ago by: Guest

Jump to the latest result

foreach

for

map

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):