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();

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Chrome 5 runs

charAt()

190.6M/s

character index

184.3M/s

startsWith()

175.6M/s

slice()

148.7M/s

RegExp

78.6M/s

Fastest: charAt() (2.4x faster)

View exact numbers

✓ charAt(): 190,605,456 ops/sec
• character index: 184,282,848 ops/sec
• startsWith(): 175,554,720 ops/sec
• slice(): 148,721,472 ops/sec
• RegExp: 78,563,272 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
character index
charAt()
startsWith()
slice()
RegExp

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year 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

charAt()

194.0M/s

startsWith()

192.4M/s

character index

184.3M/s

slice()

148.7M/s

RegExp

79.0M/s

View exact numbers

Test name	Executions per second
✓ charAt()	193,973,232 Ops/sec
startsWith()	192,369,584 Ops/sec
character index	184,282,848 Ops/sec
slice()	148,721,472 Ops/sec
RegExp	79,027,360 Ops/sec

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

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: 5 years ago by: Registered User

Go to the latest result

character index

charAt()

startsWith()

slice()

RegExp

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Chrome 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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: 5 years ago by: Registered User

Go to the latest result

character index

charAt()

startsWith()

slice()

RegExp

Historical Performance Data aggregated from 5 community runs

Desktop Results:

Chrome 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

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