Benchmark: ES6 Map - forEach vs for...of while clearing

Script Preparation code:

var myMap = new Map([[x => x, 'a'], [x => x, 'b'], [x => x, 'c'], [x => x, 'd']]);

Tests:

forEach
myMap.forEach((payload, callback) => { callback(payload); myMap.delete(callback); });
for...of
for (const [callback, payload] of myMap) { callback(payload); myMap.delete(callback); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
for...of

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

The provided JSON represents a benchmark test case for JavaScript microbenchmarks on the MeasureThat.net website. The test aims to compare the performance of two approaches for iterating over and modifying elements in a Map data structure.

**Overview**

A Map is a built-in JavaScript object that stores key-value pairs, where each key is unique and maps to a specific value. In this benchmark, we're comparing two ways to iterate over the key-value pairs in a Map:

1. **forEach**: This method iterates over the elements of an array or an object using a callback function.
2. **for...of**: This statement allows iterating over iterable objects, such as arrays and Maps.

**Options compared**

The benchmark compares the performance of these two approaches:

* **forEach**: Iterates over the key-value pairs in the Map using a callback function.
* **for...of**: Iterates over the key-value pairs in the Map using the for...of statement.

**Pros and Cons**

### forEach

Pros:

* Widely supported across browsers and environments.
* Allows for direct access to the current iteration's value and index (not applicable in this case, as we're only accessing values).

Cons:

* Can be slower due to the overhead of function calls and potential bounds checks.

### for...of

Pros:

* Can be faster due to fewer function call overheads.
* More concise and readable syntax.

Cons:

* Not all browsers support it (e.g., older versions of Internet Explorer).
* May not work correctly if the Map object's prototype chain is modified.

**Library**

There is no external library used in this benchmark. The Map data structure is a built-in JavaScript object.

**Special JS feature or syntax**

None are mentioned explicitly, but `=>` is used as an arrow function syntax (i.e., shorthand for function expressions).

**Benchmark preparation code**

The script preparation code creates a new Map instance with four key-value pairs and assigns it to the variable `myMap`. The HTML preparation code is empty.

**Individual test cases**

There are two test cases:

1. **forEach**: Iterates over the key-value pairs in `myMap` using the `forEach` method.
2. **for...of**: Iterates over the key-value pairs in `myMap` using the for...of statement.

**Latest benchmark result**

The latest benchmark results show that the **for...of** approach is slightly faster than the **forEach** approach, with an average of 14,206,932 executions per second (in Chrome 106 on a Mac OS X 10.15.7 desktop) compared to 14,245,993 executions per second.

**Other alternatives**

If you want to explore other approaches for iterating over Map elements, consider the following:

* **Array.from()**: This method converts a Map into an array and allows iteration using standard array methods (e.g., forEach).
* **Iterators**: You can create custom iterators for Maps using the `Iterator` class from JavaScript's built-in `Symbol.iterator` protocol.
* **Generators**: You can use generator functions to iterate over Map elements, which may provide better performance in certain scenarios.

Keep in mind that these alternatives might have trade-offs in terms of code readability, compatibility with older browsers, or overall performance.

Related benchmarks:

ES6 Map - forEach vs for...of while clearing (version: 0)

Comparing performance of: forEach vs for...of

Created: 3 years ago by: Guest

Jump to the latest result

forEach

for...of

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):