Benchmark: .startsWith vs .charAt for single character

HTML Preparation code:

<div></div>

Script Preparation code:

var data = window.data = [];
const possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var TOTAL_STRINGS = window.TOTAL_STRINGS = 100000;

function getRandomInt(max) {
  return Math.floor(Math.random() * max);
}

function makeRandomString(len) {
  var text = "";
  for( var i=0; i < len; i++ ) {
    text += possible.charAt(getRandomInt(possible.length));
  }
  return text;
}

while (data.length < TOTAL_STRINGS) {
  data.push(makeRandomString(getRandomInt(20)));
}

Tests:

startsWith
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var regex = window.regex; while (x < TOTAL_STRINGS) { const str = data[x]; str.startsWith("A"); x += 1; }
.charAt
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; str.charAt(0) === 'A'; x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
.charAt

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/139.0.0.0 Safari/537.36

Browser/OS: Chrome 139 on Windows

View result in a separate tab

Test name	Executions per second
startsWith	1498.9 Ops/sec
.charAt	1376.7 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark definition and explain what's being tested, along with the pros and cons of each approach.

**Benchmark Definition**

The provided benchmark is designed to compare the performance of two JavaScript functions: `startsWith` and `.charAt`. Both functions are used to check if a string starts with or contains a specific character, respectively.

**Script Preparation Code**

The script preparation code generates a large dataset of random strings using a predefined character set (`ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789`). The dataset consists of 100,000 strings, each with a random length between 1 and 20 characters. This ensures that the benchmark is not biased towards shorter or longer strings.

**Html Preparation Code**

The HTML preparation code simply includes an empty `<div>` element, which is likely used to measure the overhead of creating a new HTML document.

**Individual Test Cases**

There are two individual test cases:

1. **"startsWith"`**
This test case uses the `startsWith` function to check if each string in the dataset starts with the character 'A'.
2. **".charAt"`**
This test case uses the `.charAt` method to extract the first character of each string and compare it to the character 'A'.

**Library and Purpose**

There is no specific library mentioned in the benchmark definition, but the use of `window.data`, `window.TOTAL_STRINGS`, `window.regex`, and `window.match` suggests that these variables are defined elsewhere in the codebase. These variables likely contain arrays or objects used to store data for this benchmark.

**Pros and Cons**

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

* **"startsWith"`**
	+ Pros:
		- Simple and efficient implementation.
		- Optimized for performance, as it uses a single function call with a fixed string length.
	+ Cons:
		- May be slower for very short strings due to overhead from the `charAt` method.
* `.charAt`
	+ Pros:
		- Suitable for short strings, as it only requires accessing the first character.
	+ Cons:
		- More complex implementation, as it involves a separate function call and indexing into an array.

**Special JS Features or Syntax**

There are no specific JavaScript features or syntax mentioned in this benchmark definition. However, the use of `window` variables suggests that this code might be running in a browser environment with global variables.

**Alternatives**

If you were to rewrite this benchmark using alternative approaches, here are some options:

* Instead of generating random strings, you could use an existing string library or data source.
* You could use a different character set or encoding scheme.
* Alternatively, you could use a more complex pattern matching algorithm (e.g., regular expressions) for the `startsWith` test case.

Keep in mind that these alternatives might affect the accuracy and relevance of the benchmark results.

Related benchmarks:

.startsWith vs .charAt for single character (version: 0)

Testing some things

Comparing performance of: startsWith vs .charAt

Created: 7 years ago by: Guest

Jump to the latest result

startsWith

.charAt

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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