Benchmark: charAt vs indexOf

HTML Preparation code:

<div></div>

Script Preparation code:

window.regexStart = /^x/;
window.match = 'x';
window.matchLength = window.match.length;
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:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
charAt
startsWith

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its tests.

**Benchmark Definition**

The benchmark is designed to compare the performance of three string manipulation methods: `charAt`, `indexOf`, and `startsWith`. The test case uses a custom regex engine (`window.regexStart`) that returns `true` if the input matches a specific pattern (`/^x/`). This allows for a controlled comparison between the tested methods.

**Test Cases**

There are two individual test cases:

1. **charAt**: Tests the performance of accessing the first character of a string using the `charAt()` method.
2. **startsWith**: Tests the performance of checking if a string starts with a specific pattern using the `indexOf` method and comparing the result to 0 (true).

**Options Compared**

The benchmark compares two methods for each test case:

*   **charAt**: The original approach, which accesses the first character directly on the string.
*   **startsWith**: Uses the `indexOf` method to check if a pattern is at the beginning of the string.

**Pros and Cons**

**charAt:**

*   Pros:
    *   Direct access to the character without any additional operations.
    *   Can be more efficient for simple cases where the index is known.
*   Cons:
    *   May not be optimized for cases where the index is unknown or the string length is large.

**startsWith:**

*   Pros:
    *   Optimized for edge cases, especially when checking for patterns at the beginning of the string.
    *   Can handle longer strings and more complex patterns efficiently.
*   Cons:
    *   May involve an additional lookup (indexOf) that can introduce overhead.

**Library Usage**

The benchmark uses a custom regex engine (`window.regexStart`) to control the comparison. This library is not a standard JavaScript library, but rather a simple implementation of a regular expression that returns `true` if the input matches the pattern (`/^x/`). The purpose of this library is to provide a consistent and repeatable comparison between the tested methods.

**Special JS Features/Syntax**

There are no special features or syntax used in this benchmark. It relies on standard JavaScript features, such as functions, variables, loops, and string manipulation methods.

**Alternative Approaches**

If you're interested in exploring alternative approaches, here are a few options:

*   **Regex-based approach**: Instead of using `charAt` and `indexOf`, you can use regular expressions to extract the first character or check for patterns. This approach would involve creating a regex pattern that matches your desired behavior.
*   **String manipulation functions**: You could explore alternative string manipulation methods, such as using the `substr` method or other library functions like Lodash's `startsWith` function.

However, keep in mind that these alternatives may have different performance characteristics and might not be suitable for all use cases.

Related benchmarks:

charAt vs indexOf (version: 0)

fork of https://www.measurethat.net/Benchmarks/Show/975/11/regex-vs-indexof-vs-startswith-vs-substr

Comparing performance of: charAt vs startsWith

Created: 3 years ago by: Guest

Jump to the latest result

charAt

startsWith

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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