Benchmark: array vs charAt vs startsWith

Script Preparation code:

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

Tests:

array
if (myStr[0] === '!') noop();
charAt
if (myStr.charAt(0) === '!') noop();
startsWith
if (myStr.startsWith('!')) noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array
charAt
startsWith

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**What is being tested?**

The provided JSON represents a benchmark that compares three different approaches to check if a string starts with a specific character or substring:

1. `array`: using array indexing (`myStr[0] === '!')`
2. `charAt`: using the `charAt()` method of the String prototype (`myStr.charAt(0) === '!')`
3. `startsWith`: using the `startsWith()` method (introduced in ECMAScript 2015, also known as ES6)` (`myStr.startsWith('!'))`

**Options compared**

The three options are being compared for their performance, which is measured by the number of executions per second.

**Pros and Cons:**

1. **Array Indexing (`array`)**:
	* Pros: Simple, easy to implement, and likely to be optimized by the engine.
	* Cons: May not work correctly if `myStr` contains non-string values or is null/undefined.
2. **`charAt()` method**:
	* Pros: Wide adoption, well-documented, and relatively efficient.
	* Cons: May require additional overhead due to the function call and method invocation.
3. **`startsWith()` method** (ES6):
	* Pros: Modern, expressive, and optimized for performance.
	* Cons: Not supported in older browsers and engines, may not be as fast as the other two options.

**Library and purpose**

The `noop` variable is assigned to a function that does nothing (`Function.prototype`). Its purpose is to provide a placeholder or a no-op operation that can be used to avoid unnecessary work when testing the benchmark. In this case, it's likely being used to measure the overhead of each test case.

**Special JavaScript feature or syntax**

The `startsWith()` method was introduced in ECMAScript 2015 (ES6). It's not supported in older browsers and engines, which is why MeasureThat.net is running the benchmark on a relatively modern browser version (Firefox 103).

**Other alternatives**

If you're interested in exploring alternative approaches, here are some additional options:

* Using regular expressions (`/!/`)
* Using the `indexOf()` method with a negative offset (`myStr.indexOf('!') < 0`)
* Using a custom implementation that leverages native optimizations for string comparison (e.g., using SIMD instructions)

Keep in mind that these alternatives might not be as straightforward to implement or may have different performance characteristics.

In summary, MeasureThat.net is running a benchmark that compares three approaches to check if a string starts with a specific character: array indexing, the `charAt()` method, and the modern `startsWith()` method (ES6). The goal is to determine which approach provides the best performance.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:103.0) Gecko/20100101 Firefox/103.0

Browser/OS: Firefox 103 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
array	176574752.0 Ops/sec
charAt	159315872.0 Ops/sec
startsWith	29520006.0 Ops/sec

Related benchmarks:

array vs charAt vs startsWith (version: 0)

Comparing performance of: array vs charAt vs startsWith

Created: 3 years ago by: Guest

Jump to the latest result

array

charAt

startsWith

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):