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

Script Preparation code:

var str = '!foo bar baz';
var noop = Function.prototype;

Tests:

character index
if (str[0] === '!') noop();
charAt()
if (str.charAt(0) === '!') noop();
startsWith()
if (str.startsWith('!')) noop();
slice()
if (str.slice(0, 1) === '!') noop();
RegExp
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 28 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

The benchmark is designed to compare different methods for accessing the first character of a string in JavaScript. The test cases use various approaches:

1. **Character Index (`str[0]`)**: This method directly accesses the first element of the string as an index, which is essentially equivalent to `charAt(0)`.
2. **`charAt()`**: A built-in method that returns the character at a specified index.
3. **`startsWith()`**: A method that checks if a string starts with a certain substring or pattern.
4. **`slice()`**: A method that extracts a section of a string, in this case, taking only the first character (`str.slice(0, 1)`).
5. **`RegExp`**: A regular expression object used to match patterns at the beginning of a string.

Now, let's discuss the pros and cons of each approach:

* **Character Index**:
	+ Pros: Fast and efficient since it directly accesses memory.
	+ Cons: May not be as readable or maintainable as other methods.
* **`charAt()`**:
	+ Pros: Widely supported, easy to read, and maintainable.
	+ Cons: May incur overhead due to method call and indexing.
* **`startsWith()`**:
	+ Pros: Concise and expressive code. Can handle multiple starting characters or patterns.
	+ Cons: May be slower than direct indexing due to the additional logic.
* **`slice()`**:
	+ Pros: Flexible, as it can extract any part of a string, not just the first character.
	+ Cons: May incur overhead due to the creation of a new array and slicing process.
* **`RegExp`**:
	+ Pros: Highly expressive, allowing for complex patterns and matching rules.
	+ Cons: Can be slow due to regular expression compilation and execution.

In terms of special features or syntax, note that `startsWith()` uses a method call with a built-in function (`String.prototype.startsWith()`), which might not be immediately apparent to all users. However, the code is still relatively straightforward.

Now, let's consider other alternatives:

* **Array indexing** (e.g., using an array to store the first character of each string): This approach would have similar performance characteristics to `charAt()`.
* **Using `String.prototype.charCodeAt()`**: This method returns the Unicode code point for a single character at a specified index. While it's not as concise as `charAt()`, it could be used as an alternative.
* **Using `String.prototype.localeCompare()`**: Although designed for comparing strings lexicographically, this method can also be used to compare strings based on their first characters.

Keep in mind that the choice of approach ultimately depends on personal preference, code readability, and specific use cases. The benchmark is designed to compare these different methods in a controlled environment, providing insights into performance differences and best practices for accessing the first character of a string in JavaScript.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36

Browser/OS: Chrome 92 on Linux

View result in a separate tab

Test name	Executions per second
character index	6815497.0 Ops/sec
charAt()	6842253.0 Ops/sec
startsWith()	6790864.5 Ops/sec
slice()	6337922.5 Ops/sec
RegExp	5735900.0 Ops/sec

Related benchmarks:

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

Compare methods for testing string's beggining character.

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

Created: 3 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 28 days ago):