Benchmark: Strings starts with using startsWith, array access, slice.

Script Preparation code:

const strings = ['onclick', 'id', 'onhover', 'class'];
function getStrings(){return strings;};

Tests:

String.startsWith
let matches = 0; getStrings().forEach(str => { if(str.startsWith('on')) matches++; });
Array access []
let matches = 0; getStrings().forEach(str => { if(str[0] === 'o' && str[0] === 'n') matches++; });
String.slice
let matches = 0; getStrings().forEach(str => { if(str.slice(0, 2) === 'on') matches++; });
String.substr
let matches = 0; getStrings().forEach(str => { if(str.substr(0, 2) === 'on') matches++; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
String.startsWith
Array access []
String.slice
String.substr

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36

Browser/OS: Chrome 114 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
String.startsWith	17466708.0 Ops/sec
Array access []	20595682.0 Ops/sec
String.slice	13779066.0 Ops/sec
String.substr	10924355.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark named "Strings starts with using startsWith, array access, slice." The benchmark consists of four test cases:

1. `String.startsWith`
2. `Array access []` (square bracket notation)
3. `String.slice`
4. `String.substr`

These test cases are designed to measure the performance difference between using the `startsWith` method for strings and two alternative methods: array access (`[]`) and `slice` methods.

**Methods Compared**

1. **`String.startsWith`**: A built-in JavaScript method that checks if a string starts with a specified value.
2. **Array Access (`[]`)**: This approach uses square bracket notation to access the first character of a string.
3. **`String.slice`**: This method returns a new string containing all characters from the beginning up to, but not including, a specified index.

**Pros and Cons**

* **`String.startsWith`**:
	+ Pros: Efficient, concise, and widely supported.
	+ Cons: May have performance issues if the input strings are very long or contain many prefix characters.
* **Array Access (`[]`)**:
	+ Pros: Simple and easy to understand.
	+ Cons: Less efficient than `startsWith`, as it requires multiple character access operations.
* **`String.slice`**:
	+ Pros: Allows for flexible substring extraction, but may have performance issues if the input strings are very long.
	+ Cons: More complex and less intuitive than `startsWith`.

**Library Usage**

None of the test cases use any external libraries.

**Special JS Features or Syntax**

* None mentioned in this benchmark.

**Benchmark Results**

The provided latest benchmark result shows that:

1. `Array access []` is the slowest, with approximately 14% execution time compared to `String.startsWith`.
2. `String.slice` has a moderate performance, around 22% slower than `String.startsWith`.
3. `String.startsWith` is the fastest.

**Other Alternatives**

If you're interested in exploring alternative methods for string prefix checks or array access, some other options include:

* Using regular expressions (`/^[^on]/` for `startsWith`, `/^\w{2,3}/` for `[]`)
* Employing custom implementation using bitwise operations (e.g., checking the first two characters as an unsigned 16-bit integer)
* Leveraging native methods like `match()` or `indexOf()` for more complex prefix matching

Keep in mind that these alternatives might not offer significant performance improvements and may introduce additional complexity.

I hope this explanation helps you understand the benchmark's purpose and methodology!

Related benchmarks:

Strings starts with using startsWith, array access, slice. (version: 0)

Comparing performance of: String.startsWith vs Array access [] vs String.slice vs String.substr

Created: one year ago by: Registered User

Jump to the latest result

String.startsWith

Array access []

String.slice

String.substr

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):