Benchmark: forEach vs For of and startsWith 2

Script Preparation code:

var strs = [
    '',
    '*',
    '#',
    '*short',
    '#short',
    '*'.padEnd(2500, '-'),
    '#'.padEnd(2500, '-'),
];

Tests:

.startsWith forEach
strs.forEach(str => {str.startsWith('*')})
.charAt forEach
strs.forEach(str => {str.charAt(0) === '*'})
[0] forEach
strs.forEach(str => {str[0] === '*'})
.match forEach
strs.forEach(str => {str.match(/^\*/)})
.startsWith
for(const str of strs) {str.startsWith('*')}
.charAt
for(const str of strs) {str.charAt(0) === '*'}
[0]
for(const str of strs) {str[0] === '*'}
.match
for(const str of strs) {str.match(/^\*/)}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.startsWith forEach
.charAt forEach
[0] forEach
.match forEach
.startsWith
.charAt
[0]
.match

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript benchmark test case created on MeasureThat.net. The test compares the performance of various loops and methods (forEach, for...of, charAt, etc.) to access the first character of an array of strings.

**Test Cases**

There are eight individual test cases:

1. **.startsWith forEach**: Tests the `forEach` method with a callback function that uses `str.startsWith('*')`.
2. **.charAt forEach**: Tests the `forEach` method with a callback function that uses `str.charAt(0) === '*'`.
3. **[0] forEach**: Tests the `forEach` method with a callback function that uses `str[0] === '*'`.
4. **.match forEach**: Tests the `forEach` method with a callback function that uses `str.match(/^\\*/)`.
5. **.startsWith**: Tests the `startsWith` method without using `forEach`.
6. **.charAt**: Tests the `charAt` method without using `forEach`.
7. **[0]**: Tests the array indexing approach without using `forEach`.
8. **.match**: Tests the regular expression matching approach without using `forEach`.

**Comparison of Loops and Methods**

The test case compares the performance of different loops and methods to access the first character of an array of strings:

*   **`forEach`**: A loop that iterates over each element in the array, applying a callback function to each element.
*   **`for...of`**: A loop that iterates over each element in the array using a `for...of` loop declaration.
*   **`charAt`** and **`[0]`**: Array indexing methods that directly access the first character of an element.
*   **`.match` with regular expressions**: Regular expression matching to extract the first character.

**Options Compared**

The test case compares various options for accessing the first character of an array of strings:

*   Looping using `forEach`, `for...of`, and direct array indexing (`[0]`).
*   Using callback functions or arrow functions with `forEach`.
*   Using regular expression matching to extract the first character.

**Pros and Cons of Each Approach**

Here are some pros and cons of each approach:

*   **Looping using `forEach`**: Easy to implement, but can be slower due to the overhead of iterating over an array.
    *   Pros: Simple implementation, good for demonstrating iteration patterns.
    *   Cons: Potential performance impact.
*   **Looping using `for...of`**: Similar to `forEach`, but with a more traditional loop syntax. Can be faster due to the optimized JavaScript engine.
    *   Pros: Good performance, easy to understand.
    *   Cons: May require additional setup for array iteration.
*   **`charAt`** and **`[0]`**: Direct array indexing methods that can be fast if implemented correctly.
    *   Pros: Fast execution, simple implementation.
    *   Cons: May not work with non-string elements or arrays with more than one element.
*   **`.match` with regular expressions**: Can be slow due to the overhead of compiling and executing a regular expression.
    *   Pros: Flexible for string manipulation tasks.
    *   Cons: Potential performance impact.

**Conclusion**

This benchmark test case provides insight into the performance differences between various loops and methods for accessing the first character of an array of strings. By understanding these trade-offs, developers can choose the most efficient approach for their specific use cases.

Here are some key takeaways from this test:

*   For simple string manipulation tasks, direct array indexing (`[0]`) or using `charAt` may be the fastest options.
*   Looping using `forEach` or `for...of` can be a good alternative to direct array indexing, offering better performance and easier implementation for complex iteration patterns.
*   Regular expression matching with `.match` can be useful for more complex string manipulation tasks, but should be used judiciously due to its potential performance impact.

**Next Steps**

For future improvements or modifications to this benchmark test case, consider:

*   Adding more test cases to cover other aspects of JavaScript iteration and array operations.
*   Using different data sets (e.g., large arrays, arrays with multiple types) to better understand the performance implications.
*   Analyzing the results in detail using tools like console logs or debugging tools to gain deeper insights into the execution patterns.

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.6 Safari/605.1.15

Browser/OS: Safari 17 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
.startsWith forEach	3857820.8 Ops/sec
.charAt forEach	8148024.0 Ops/sec
[0] forEach	7509406.5 Ops/sec
.match forEach	3467860.0 Ops/sec
.startsWith	3963526.0 Ops/sec
.charAt	9492885.0 Ops/sec
[0]	8493414.0 Ops/sec
.match	7197429.5 Ops/sec

Related benchmarks:

forEach vs For of and startsWith 2 (version: 0)

Taken from https://jsbench.me/welq15149d/1. Testing forEach vs For of, while also testing first character

Comparing performance of: .startsWith forEach vs .charAt forEach vs [0] forEach vs .match forEach vs .startsWith vs .charAt vs [0] vs .match

Created: 2 months ago by: Guest

Jump to the latest result

.startsWith forEach

.charAt forEach

[0] forEach

.match forEach

.startsWith

.charAt

[0]

.match

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):