Benchmark: for vs foreach vs for..of vs for cached

Script Preparation code:

var array = new Array(100);

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmark test case for comparing the performance of different loop iteration methods: `for`, `foreach`, `for cached`, and `for..of`.

**Loop Iteration Methods**

1. **For**: The traditional `for` loop uses an explicit counter variable (`i`) to iterate over the array. This method requires manual incrementing of the counter variable.
2. **Foreach**: The `forEach` method is a part of the ECMAScript 2015 (ES6) standard and allows iterating over arrays using a callback function. It iterates over each element in the array, but does not provide direct access to the index or length of the array.
3. **For Cached**: This variation of the `for` loop uses two counter variables: one for the iteration (`i`) and another for the array length (`n`). This method is similar to the traditional `for` loop but avoids re-calculating the array length on each iteration.
4. **For Of**: The `for..of` loop is a part of ES6 and allows iterating over arrays using a direct access to each element without the need for an index variable.

**Comparison and Performance**

The provided benchmark test case compares the performance of these four loop iteration methods:

*   **For**: This method has the highest overhead due to manual incrementing of the counter variable.
*   **Foreach**: This method is optimized for array iteration but can be slower than other methods due to the callback function execution and potential array length calculations.
*   **For Cached**: This method avoids re-calculating the array length on each iteration, resulting in improved performance compared to traditional `for` loops.
*   **For Of**: This method provides direct access to each element without needing an index variable, making it potentially faster than other methods.

**Library and Special Features**

There are no libraries used in this benchmark test case. However, the ECMAScript 2015 (ES6) standard is utilized for the `forEach` and `for..of` loop methods.

**Other Considerations**

When working with loops in JavaScript:

*   **Avoid manual incrementing of counter variables**, as it can lead to performance issues.
*   **Use array lengths directly**, rather than calculating them on each iteration, to avoid unnecessary computations.
*   **Take advantage of optimized methods**, such as `forEach` and `for..of`, which are designed for efficient array iteration.

**Alternatives**

For similar benchmark test cases:

*   MeasureThat.net provides a wide range of JavaScript microbenchmarks, including tests for array operations, string manipulation, and more.
*   Other popular benchmarking tools include:
    *   Benchmark.js: A lightweight, modular benchmarking library.
    *   jsperf: A simple, fast benchmarking tool specifically designed for Node.js.
    *   Google's Closure Compiler: A source-to-source compiler that can also be used as a performance optimizer.

Keep in mind that different benchmarks may prioritize specific aspects of JavaScript performance.

Related benchmarks:

for vs foreach vs for..of vs for cached (version: 0)

Compare loop performance

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

Created: 3 years ago by: Guest

Jump to the latest result

for

foreach

for cached

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):