Benchmark: for vs foreach vs for..in vs for..of - fork

Script Preparation code:

var array = new Array(100000);

Tests:

for
for (var i = 0; i < array.length; i++) { array[i]; }
foreach
array.forEach(function(i) { array[i]; });
for in
for (var i in array) { array[i]; }
for..of
for (var i of array) { array[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to compare the performance of four different loop constructs:

1. Traditional `for` loop
2. `forEach` method
3. `for...in` loop
4. `for...of` loop

**Loop Constructs Comparison**

Here's a brief explanation of each loop construct and their pros and cons:

### 1. Traditional `for` Loop

```javascript
for (var i = 0; i < array.length; i++) {
  array[i];
}
```

Pros: Easy to read, maintain, and write.

Cons: Can lead to variable naming issues (`i`) if not explicitly declared as `let`, `const`, or `var`.

### 2. `forEach` Method

```javascript
array.forEach(function(i) {
  array[i];
});
```

Pros:

* Cleaner and more concise syntax.
* Less prone to variable naming issues.

Cons: Can be slower than traditional loops due to the function invocation overhead, especially for large arrays.

### 3. `for...in` Loop

```javascript
for (var i in array) {
  array[i];
}
```

Pros:

* Works with both indexed and non-indexed arrays.
* Less prone to variable naming issues.

Cons: May iterate over properties other than those of the array itself, leading to unexpected behavior. Additionally, it's not suitable for use with modern JavaScript arrays (arrays created using `Array.prototype.push` or `Array.from()`).

### 4. `for...of` Loop

```javascript
for (var i of array) {
  array[i];
}
```

Pros:

* Cleaner and more concise syntax.
* Works specifically with arrays, avoiding potential issues with non-indexed properties.

Cons: Limited support in older browsers, as it was introduced in ECMAScript 2015. It also has some quirks when used with certain types of arrays (e.g., `Array.from()`).

**Library Usage**

There is no explicit library mentioned in the benchmark definition. However, note that if any libraries are used in the test cases, they would be excluded from this analysis.

**Special JavaScript Features**

The benchmark does not explicitly use any special JavaScript features beyond what's covered in the loop constructs comparison. If you'd like to explore more advanced topics, feel free to ask!

**Alternatives and Considerations**

If you're interested in exploring alternative loop constructs or optimization techniques, here are a few options:

1. `for...of` loops with array-like objects (e.g., using `Array.from()` or `Object.values()`).
2. Array methods like `map()`, `reduce()`, or `filter()`.
3. Using Web Workers or worker threads for parallel processing.
4. Optimizing memory allocation and reuse for large arrays.

Keep in mind that each alternative has its own trade-offs, performance characteristics, and compatibility considerations.

If you have any further questions or would like to discuss specific aspects of the benchmark, feel free to ask!

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 Safari/605.1.15

Browser/OS: Safari 16 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for	178.2 Ops/sec
foreach	523.1 Ops/sec
for in	30777.8 Ops/sec
for..of	202.7 Ops/sec

Related benchmarks:

for vs foreach vs for..in vs for..of - fork (version: 0)

Compare loop performance

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

Created: one year ago by: Guest

Jump to the latest result

for

foreach

for in

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):