Benchmark: startsWith vs charCodeAt

Script Preparation code:

str = "hello world"

Tests:

startsWith
str.startsWith('he') === true
charCodeAt
str.charCodeAt(0) === 104

Historical Performance Data aggregated from 6 community runs

Desktop Results:

Chrome 6 runs

charCodeAt

127.9M/s

startsWith

122.6M/s

View exact numbers

✓ charCodeAt: 127,868,224 ops/sec
• startsWith: 122,575,056 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
charCodeAt

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/146.0.0.0 Safari/537.36

Browser/OS: Chrome 146 on Mac OS X 10.15.7

View result in a separate tab

charCodeAt

272.9M/s

startsWith

240.0M/s

View exact numbers

Test name	Executions per second
✓ charCodeAt	272,865,824 Ops/sec
startsWith	239,979,024 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in this JavaScript benchmark.

**Benchmark Overview**

The benchmark is designed to compare the performance of two different approaches: `str.startsWith('he')` and `str.charCodeAt(0) === 104`. The goal is to determine which approach is faster on a variety of devices, including iPhones.

**Options Compared**

Two options are being compared:

1. **`str.startsWith('he')`**: This method checks if the string `str` starts with the characters `'he'`.
2. **`str.charCodeAt(0) === 104`**: This method converts the first character of the string `str` to its corresponding ASCII code (104 for 'h') and then compares it to 104.

**Pros and Cons**

*   **`str.startsWith('he')`**:
    *   Pros: Simple, straightforward, and easy to understand. It's a common pattern used in many applications.
    *   Cons: May be slower due to the string search operation.
*   **`str.charCodeAt(0) === 104`**:
    *   Pros: Can be faster because it uses an ASCII code lookup table, which is optimized for performance.
    *   Cons: Requires understanding of ASCII codes and may not work as expected with non-ASCII characters.

**Library and Purpose**

In this benchmark, the `charCodeAt()` method is part of the JavaScript standard library, which provides a way to access the Unicode code point for each character in a string. This method is useful when you need to perform operations based on the ASCII or Unicode value of a character.

**Special JS Feature or Syntax**

There doesn't appear to be any special JavaScript feature or syntax being used in this benchmark that requires deep knowledge of JavaScript.

**Other Alternatives**

If you want to create similar benchmarks, you can use tools like Benchmark.js, which provides a simple way to write and run benchmarks. You can also consider using libraries like BenchmarkSuite or Jest, which offer more advanced features for writing and running benchmarks.

In summary, this benchmark is designed to compare the performance of two different approaches: `str.startsWith('he')` and `str.charCodeAt(0) === 104`. The `charCodeAt()` method uses an ASCII code lookup table, making it potentially faster than the string search operation used in `startsWith()`.

startsWith vs charCodeAt (version: 0) Benchmark.js

Comparing performance of: `startsWith vs charCodeAt`

Created: 3 years ago by: Guest

Go to the latest result

startsWith

charCodeAt

Historical Performance Data aggregated from 6 community runs

Desktop Results:

Chrome 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

startsWith vs charCodeAt (version: 0) Benchmark.js

Comparing performance of: startsWith vs charCodeAt

Created: 3 years ago by: Guest

Go to the latest result

startsWith

charCodeAt

Historical Performance Data aggregated from 6 community runs

Desktop Results:

Chrome 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Comparing performance of: `startsWith vs charCodeAt`