Benchmark: For Loop vs For Of in iterating strings

Script Preparation code:

function validCharForL(s){
  const n='"*/:<>?\\|';
  let r="";
  for(let i=0,l=s.length;i<l;i++)
    r+=n.includes(s[i])?String.fromCharCode(s.charCodeAt(i)+65248):s[i];
  return r
};

function validCharForOf(s){
  const n='"*/:<>?\\|';
  let r="";
  for(let c of s)
    r+=n.includes(c)?String.fromCharCode(c.charCodeAt()+65248):c;
  return r
};

Tests:

For Loop
for (let i = 0; i < 1000; i++) validCharForL("1234*/:<abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234");
For Of
for (let i = 0; i < 1000; i++) validCharForOf("1234*/:<abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For Loop
For Of

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Browser/OS: Chrome 107 on Linux

View result in a separate tab

Test name	Executions per second
For Loop	322.7 Ops/sec
For Of	288.4 Ops/sec

Autogenerated LLM Summary (model gemma2:9b, generated 2 months ago):

LLMs can make mistakes. Check important info.

This benchmark compares the performance of two methods for iterating over a string in JavaScript: a traditional `for` loop and a `for...of` loop.

**Here's what each method does:**

* **`validCharForL(s)` (using a `for` loop):**
    1. Defines a string `n` containing characters considered invalid for Windows and Linux file paths.
    2. Iterates through the input string `s` using a `for` loop, accessing each character by its index (`i`).
    3. For each character:
       * It checks if the character is present in the `n` string (using `includes`).
       * If it is, it applies Unicode code point conversion (adding 65248) to "full-width" the character. This simulates how some special characters are displayed on certain systems.
       * Otherwise, it keeps the original character.
    4. Returns the modified string `r`.

* **`validCharForOf(s)` (using a `for...of` loop):**
   1. Performs the same initial setup as the `for` loop version.
   2. Iterates through each character (`c`) in the input string `s` directly using a `for...of` loop. 
   3. For each character `c`:
      * It checks if `c` is present in the `n` string (using `includes`).
      * If it is, applies Unicode code point conversion and retains the modified character.
      * Otherwise, keeps the original character.
    4. Returns the modified string `r`.

**Comparison:**

| Approach | `for` loop | `for...of` loop |
|---|---|---|
| **Syntax** | More verbose; requires explicit index management. | Simpler and more concise; iterates directly over values. |
| **Performance** | Can be slightly faster in some cases due to potentially lower overhead for accessing elements by index. However, the difference is often negligible. | Generally considered easier to read and maintain, and often performs comparably to `for` loops in modern JavaScript engines. |

**Alternatives:**

* **Array methods:**  JavaScript provides array methods like `.map()` and `.forEach()` which can be used for similar tasks. They often have optimized implementations within the engine and might offer better performance than explicit loops in certain scenarios. 
    * Example: `s.split('').map(c => n.includes(c) ? String.fromCharCode(c.charCodeAt() + 65248) : c).join('');`

**Key Takeaways:**

* The choice between a `for` loop and a `for...of` loop often comes down to readability and personal preference.
* Modern JavaScript engines are highly optimized, so the performance difference between these loops is usually not significant in most practical applications.

Related benchmarks:

For Loop vs For Of in iterating strings (version: 0)

validCharForL() and validCharForOf() iterate through a string and full-width any characters invalid for Windows and Linux, using, respectively, a for loop and a for of loop.

Comparing performance of: For Loop vs For Of

Created: 2 years ago by: Registered User

Jump to the latest result

For Loop

For Of

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gemma2:9b, generated 2 months ago):