Benchmark: for vs foreach for (cached length) vs for..of -- With assignment

Script Preparation code:

var array = new Array(100);
for (var i = 0; i < array.length; i++) {
  array[i] = i * 10000
}

Tests:

for
for (let i = 0; i < array.length; i++) { array[i] + 1 }
foreach
array.forEach((i) => { array[i] + 1 });
for (cached length)
for (let i = 0, length = array.length; i < length; i++) { array[i] + 1 }
for..of
for (var i of array) { array[i] + 1 }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
foreach
for (cached length)
for..of

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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**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark compares the performance of four different loop constructs: traditional `for` loops, `foreach` loops, and two variations of `for` loops with caching: one that uses a cached variable for the array length, and another that uses the `of` syntax.

**What is tested?**

The test case measures the execution speed (measured in executions per second) of each loop construct as they iterate over an array of 100 elements. The array is populated with values using the initial script preparation code: `array[i] = i * 10000`. In each iteration, a simple increment operation is performed on each element: `array[i] + 1`.

**Options compared**

The four loop constructs are compared as follows:

* **Traditional `for` loops**: A classic loop construct that uses a manually incremented index variable.
* **`foreach` loops**: A loop construct that iterates over an array using the `forEach` method, which is equivalent to a traditional `for` loop but with a more concise syntax.
* **`for (cached length)`**: A variation of the traditional `for` loop that uses a cached variable for the array length, reducing the overhead of recalculating the length in each iteration.
* **`for..of` loops**: A modern loop construct introduced in ECMAScript 2015, which allows iterating over an array using a more concise syntax.

**Pros and cons**

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

* **Traditional `for` loops**:
	+ Pros: Well-established, easy to understand, and widely supported.
	+ Cons: Can be verbose, especially for large arrays or complex iterations.
* **`foreach` loops**:
	+ Pros: Concise syntax, easier to read, and less prone to errors.
	+ Cons: May have performance overhead due to the `forEach` method invocation.
* **`for (cached length)`**:
	+ Pros: Reduces the overhead of recalculating the array length in each iteration.
	+ Cons: Requires careful management of the cached variable, as it may lead to out-of-scope issues if not handled correctly.
* **`for..of` loops**:
	+ Pros: Concise syntax, easier to read, and eliminates the need for manual index management.
	+ Cons: May have performance overhead due to the additional function call, although this is typically negligible.

**Library usage**

None of the loop constructs use any external libraries. The `forEach` method is a built-in JavaScript method that iterates over an array using a callback function.

**Special JS features or syntax**

There are no special JavaScript features or syntax used in this benchmark. However, it's worth noting that the `for..of` loop uses a new syntax introduced in ECMAScript 2015, which may not be supported by older browsers or environments.

**Alternatives**

If you're looking for alternatives to these loop constructs, here are a few options:

* **While loops**: A more general-purpose loop construct that can be used for both array and conditional iterations.
* **`map`, `filter`, and `reduce` methods**: These methods provide an alternative way to process arrays using functional programming principles.

Keep in mind that each of these alternatives has its own trade-offs and performance characteristics, which may affect the outcome of this benchmark.

Related benchmarks:

for vs foreach for (cached length) vs for..of -- With assignment (version: 0)

Compare loop performance

Comparing performance of: for vs foreach vs for (cached length) vs for..of

Created: 5 years ago by: Guest

Jump to the latest result

for

foreach

for (cached length)

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):