Benchmark: Iterating over string

Script Preparation code:

var test = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Quisque pretium, neque vitae varius imperdiet, sem sapien lobortis libero, a pulvinar magna ligula sit amet ante. Mauris interdum laoreet tortor, quis euismod ante accumsan in. Curabitur viverra quam quam, id dapibus justo fermentum lacinia. Pellentesque accumsan ultrices massa non volutpat. Vivamus pretium id diam sed auctor. Cras augue odio, bibendum non est at, molestie pellentesque sapien. Sed quis odio tempus, semper lectus a, luctus metus. Donec euismod vitae nibh at aliquam. Praesent mauris dui, pretium vel interdum eu, condimentum in mauris. Integer pellentesque sapien a nunc finibus, sed pellentesque nisl tempor.';
var chars = [];

Tests:

Indexed access
for (let i = 0; i < test.length; i++) { const c = test[i]; chars.push(c); }
charCodeAt
for (let i = 0; i < test.length; i++) { const c = test.charCodeAt(i); chars.push(c); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Indexed access
charCodeAt

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36 OPR/102.0.0.0

Browser/OS: Opera 102 on Windows

View result in a separate tab

Test name	Executions per second
Indexed access	13223.2 Ops/sec
charCodeAt	13412.4 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the test case and explain what's being tested.

**Overview**

The provided JSON represents a benchmark test for iterating over a string in JavaScript. The test consists of two individual test cases: "Indexed access" and "charCodeAt".

**Options Compared**

The two options compared are:

1. **Indexed access**: This approach iterates over the string using indexing (e.g., `test[i]`).
2. **charCodeAt**: This approach uses the `charCodeAt()` method to get the Unicode code point of each character in the string and then pushes it into an array.

**Pros and Cons**

**Indexed Access:**

Pros:

* Generally faster, as it avoids the overhead of calling a method.
* Can be optimized by using a cache or a lookup table for common indices.

Cons:

* May not work correctly if the string is very large, as indexing can become slow due to cache misses.
* Requires manual memory management to allocate space for the result array.

**charCodeAt:**

Pros:

* More efficient for very large strings, as `charCodeAt()` can take advantage of the CPU's caching mechanism.
* Less prone to performance issues caused by cache misses.

Cons:

* Adds overhead due to method calls, which can be slower than direct indexing.
* May not work correctly if the string contains non-ASCII characters or special values that affect `charCodeAt()` behavior.

**Library**

None are explicitly mentioned in the provided JSON. However, the use of `let` and `const` declarations suggests that the benchmark is using modern JavaScript features from ECMAScript 2015 (ES6) onwards.

**Special JS Feature or Syntax**

The test does not rely on any special JavaScript features or syntax beyond what's required for iteration and array manipulation.

**Other Considerations**

To optimize performance, it's essential to consider factors such as:

* Cache locality: Minimizing cache misses by using contiguous memory access can improve performance.
* Branch prediction: Avoiding unnecessary branches (e.g., in indexing) can help the CPU predict the next instruction.
* Memory allocation: Allocating sufficient memory for the result array can reduce overhead.

**Alternatives**

Other approaches to iterating over a string could include:

* Using `String.prototype.forEach()` or `Array.prototype.forEach()`
* Implementing a custom iterator using `Symbol.iterator` and a generator function
* Utilizing specialized libraries or frameworks that provide optimized string iteration implementations

Keep in mind that the optimal approach may depend on the specific use case, performance requirements, and available resources.

Related benchmarks:

Iterating over string (version: 1)

Comparing performance of: Indexed access vs charCodeAt

Created: 6 years ago by: Registered User

Jump to the latest result

Indexed access

charCodeAt

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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