Benchmark: char index vs charAt() vs slice() vs startsWith() vs RegExp --

Script Preparation code:

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

Tests:

character index
if (str[0] === '!') noop();
charAt()
if (str.charAt(0) === '!') noop();
startsWith()
if (str.startsWith('!')) noop();
slice()
if (str.slice(0, 1) === '!') noop();
RegExp
const pattern = /^!/; if (pattern.test(str)) noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
character index
charAt()
startsWith()
slice()
RegExp

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
character index	184282848.0 Ops/sec
charAt()	193973232.0 Ops/sec
startsWith()	192369584.0 Ops/sec
slice()	148721472.0 Ops/sec
RegExp	79027360.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON and explain the options, their pros and cons, and other considerations.

**Benchmark Definition:**
The benchmark compares methods for testing a string's beginning character. The goal is to determine which method is the fastest.

**Options:**

1. **Character Index (str[0])**:
	* This option uses direct indexing of the string to access the first character.
	* Pros: Fast, efficient, and straightforward.
	* Cons: May not work correctly if the string has a length of 0 or if the index is out of bounds.
2. **charAt()**:
	* This option uses the `charAt()` method provided by the String prototype to access the first character.
	* Pros: More robust than direct indexing, as it handles edge cases like empty strings and out-of-bounds indices.
	* Cons: May be slower than direct indexing due to additional overhead.
3. **startsWith()**:
	* This option uses the `startsWith()` method provided by the String prototype to check if the string starts with a certain character or substring.
	* Pros: More flexible than direct indexing, as it can handle strings of different lengths and substrings.
	* Cons: May be slower than direct indexing due to additional overhead and potential regular expression compilation.
4. **slice()**:
	* This option uses the `slice()` method provided by the String prototype to extract a subset of characters from the string (in this case, just the first character).
	* Pros: More flexible than direct indexing, as it can handle strings of different lengths and substrings.
	* Cons: May be slower than direct indexing due to additional overhead.
5. **RegExp**:
	* This option uses a regular expression pattern (`^!`) to match the string and extract the first character.
	* Pros: Highly flexible and powerful, but may also be slow due to the overhead of compiling and executing the regex pattern.
	* Cons: May have performance issues if the regex pattern is complex or used for large strings.

**Library Used:**
None explicitly mentioned in the provided JSON. However, the `charAt()`, `slice()`, and `startsWith()` methods are part of the String prototype, which is a built-in JavaScript object. The `RegExp` option uses a regular expression library, but it's not explicitly named or imported.

**Special JS Features/Syntax:**
None mentioned in the provided JSON.

**Other Considerations:**

* The benchmark measures the number of executions per second (ExecutionsPerSecond) for each option, which provides an indication of performance.
* The results are reported for different browsers and devices, which may be relevant if you're interested in optimizing for specific user environments.
* The benchmark doesn't consider other factors that might affect performance, such as memory usage or caching.

**Alternatives:**

* Other string manipulation methods could be used instead of the options listed above (e.g., using `indexOf()` or `localeCompare()`) or alternative libraries like Lodash.
* Regular expressions can be more powerful than the String prototype methods but may also have performance issues for large strings or complex patterns.
* If you need to optimize for specific use cases, consider profiling and benchmarking with a test runner like Jest or Mocha.

Keep in mind that these are general explanations, and the specifics of your project may vary.

Related benchmarks:

char index vs charAt() vs slice() vs startsWith() vs RegExp -- (version: 0)

Compare methods for testing string's beggining character.

Comparing performance of: character index vs charAt() vs startsWith() vs slice() vs RegExp

Created: 4 years ago by: Registered User

Jump to the latest result

character index

charAt()

startsWith()

slice()

RegExp

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):