Benchmark: char index vs charAt() vs slice() vs startsWith() vs RegExp bmk2

Tests:

character index
const str = '!foo bar baz'; const noop = Function.prototype; if (str[0] === '!') noop();
charAt()
const str = '!foo bar baz'; const noop = Function.prototype; if (str.charAt(0) === '!') noop();
startsWith()
const str = '!foo bar baz'; const noop = Function.prototype; if (str.startsWith('!')) noop();
slice()
const str = '!foo bar baz'; const noop = Function.prototype; if (str.slice(0, 1) === '!') noop();
RegExp
const str = '!foo bar baz'; const noop = Function.prototype; const pattern = /^!/; if (pattern.test(str)) noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
character index
charAt()
startsWith()
slice()
RegExp

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Overview**

The benchmark measures the performance of different methods to test if a string starts with a specific character:

1. `char index` (using square bracket notation `[0]`)
2. `charAt()` (using the `charAt()` method)
3. `slice()` (using the `slice()` method)
4. `RegExp`

**Options Compared**

Each of these methods compares how efficient they are in terms of execution speed, with the fastest method being considered the best.

Here's a brief overview of each method:

1. **`char index`**: This method uses square bracket notation `[0]` to access the first character of the string. It's simple and straightforward but may incur overhead due to string indexing.
2. **`charAt()`**: This method uses the `charAt()` method to retrieve the first character of the string. It's more explicit than the `char index` method but might be slower due to function call overhead.
3. **`slice()`**: This method uses the `slice()` method with a start index of 0 and an end index of 1 to extract the first character of the string. It can be efficient if the string is very long, as it avoids creating a new string object.
4. **`RegExp`**: This method uses a regular expression (`/!\s*/`) to match the string against a pattern that starts with `!`. If the pattern matches, the function executes.

**Pros and Cons of Each Method**

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

1. **`char index`**
	* Pros: Simple, fast, and straightforward.
	* Cons: May incur overhead due to string indexing.
2. **`charAt()`**
	* Pros: Explicit and easy to understand.
	* Cons: Might be slower due to function call overhead.
3. **`slice()`**
	* Pros: Efficient for long strings, as it avoids creating a new string object.
	* Cons: Requires specifying start and end indices, which might add complexity.
4. **`RegExp`**
	* Pros: Flexible pattern matching capabilities.
	* Cons: May incur overhead due to regular expression compilation and execution.

**Library and Special JS Feature**

The benchmark uses the `Function.prototype` object, which is a part of the JavaScript language specification. It's not a library per se, but rather a built-in feature used as a "noop" (no operation) function in the benchmark code.

No special JavaScript features or syntax are mentioned in the benchmark.

**Alternatives**

If you're interested in optimizing string manipulation performance, here are some alternative approaches:

1. **Use `String.prototype.startsWith()`**: This method is more concise and readable than using `RegExp`.
2. **Use a custom indexing function**: You can create a custom indexing function that uses bit manipulation or other optimization techniques to improve performance.
3. **Optimize string storage**: If you're working with very large strings, consider optimizing string storage by using a buffer-based approach or leveraging modern JavaScript features like `TextEncoder`.

Keep in mind that the best approach depends on your specific use case and requirements. MeasureThat.net provides a useful baseline for comparing different methods, but it's essential to experiment and optimize further based on your specific needs.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Safari/605.1.15

Browser/OS: Safari 15 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
character index	4956845.5 Ops/sec
charAt()	4996882.5 Ops/sec
startsWith()	4486130.5 Ops/sec
slice()	5008602.0 Ops/sec
RegExp	4495790.5 Ops/sec

Related benchmarks:

char index vs charAt() vs slice() vs startsWith() vs RegExp bmk2 (version: 0)

Compare methods for testing string's beggining character.

Comparing performance of: character index vs charAt() vs startsWith() vs slice() vs RegExp

Created: 2 years ago by: Guest

Jump to the latest result

character index

charAt()

startsWith()

slice()

RegExp

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):