Benchmark: for vs for in vs for of vs forEach

Script Preparation code:

var data = [... new Array(1000)].map((x,i) => i);

Tests:

forEach
let result = 0; data.forEach(x => { result = x; });
for of
let result = 0; for (let x of data) { result = x; }
for in
let result = 0; for (let i in data) { result = data[i]; }
for
let result = 0; for (let i = 0; i < data.length; i++) { result = data[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
for of
for in
for

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

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Let's break down the provided benchmark and explain what's being tested, compared, and analyzed.

**Benchmark Definition**

The benchmark is defined by two parts:

1. **Script Preparation Code**: This code snippet is used to prepare the data for the benchmark. In this case, it creates an array of 1000 elements with incremental indices using the `map()` method.
2. **Html Preparation Code**: This field is empty, which means no HTML preparation code is required.

**Individual Test Cases**

The benchmark consists of four test cases, each testing a different loop iteration:

1. **`forEach`**: Uses the `forEach()` method to iterate over the array and assign the value to a variable.
2. **`for of`**: Uses the `for...of` loop syntax to iterate over the array and assign the value to a variable.
3. **`for in`**: Uses the `for...in` loop syntax to iterate over the array's indices and assign the value to a variable.
4. **`for`**: Uses the traditional `for` loop syntax with an index variable to iterate over the array and assign the value to a variable.

**Library Usage**

None of the test cases use any external libraries, which means that the results are solely dependent on the JavaScript engine's implementation.

**Special JS Features or Syntax**

Only one test case, **`forEach`**, uses a special syntax (`forEach()`) that is not part of the traditional `for` loop structure. The `for...of` loop is also a special syntax introduced in ECMAScript 2015 (ES6).

**Other Considerations**

The benchmark measures the execution time per second for each test case, which indicates how quickly each loop iteration can be executed.

**Comparison and Pros/Cons**

Each loop iteration has its own strengths and weaknesses:

* **`forEach()`**: This method is concise and easy to read, but it may incur a slight performance overhead due to the function call.
* **`for of`**: This syntax is modern and efficient, as it avoids the need for an explicit index variable. However, some older JavaScript engines might not support it natively.
* **`for in`**: This loop is less efficient than `for...of` or traditional `for` loops due to its reliance on iterating over indices rather than actual values.
* **Traditional `for`**: While straightforward and easy to understand, this loop structure may be slower than the other options due to the overhead of updating an index variable.

**Alternatives**

If you were to rewrite these benchmarks using different languages or frameworks, here are some alternatives:

* For a Python equivalent, use list comprehension or the `enumerate()` function.
* For a Java equivalent, use traditional `for` loops with indexes.
* For a C++ equivalent, use iterators or traditional `for` loops.

Keep in mind that each language has its unique performance characteristics and optimization strategies.

Related benchmarks:

for vs for in vs for of vs forEach (version: 0)

Comparing performance of: forEach vs for of vs for in vs for

Created: 4 years ago by: Guest

Jump to the latest result

forEach

for of

for in

for

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):