Benchmark: String test comparison

Script Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON benchmark.

The goal of this benchmark is to compare different ways of checking if a string starts with a specific character, represented by the exclamation mark (!) symbol. The test aims to determine which method is the fastest among various approaches.

**Options compared:**

1. **Using square bracket indexing (`str[0] === '!')**: This approach directly accesses the first character of the string using square brackets and checks if it's equal to the exclamation mark.
2. **Using `charAt(0)`**: This method uses the `charAt` function to get the character at index 0 of the string, which is equivalent to the previous approach.
3. **Using `startsWith('!')`**: This approach leverages a built-in String method called `startsWith`, which returns true if the string starts with the specified value (in this case, '!').
4. **Using regular expressions (`pattern.test(str)`)**: A more explicit way of checking if a string matches a pattern using a RegExp object.
5. **Using slicing (`str.slice(0, 1) === '!')**: This method extracts the first character from the string using `slice` and checks if it's equal to the exclamation mark.

**Pros and Cons:**

* **Square bracket indexing (`str[0] === '!')`**: Fast, but may not work as expected with non-string values or objects that don't support bracket notation.
* **Using `charAt(0)`**: Similar to square bracket indexing, fast, but may have similar limitations.
* **Using `startsWith('!')`**: Convenient and readable, built-in method, but might be slower due to its nature (it has to iterate over the string).
* **Using regular expressions (`pattern.test(str)`)**: Flexible, powerful, but can be slow due to the overhead of parsing and executing the RegExp pattern.
* **Using slicing (`str.slice(0, 1) === '!')**: Similar to square bracket indexing and `charAt(0)`, fast, but may have similar limitations.

**Library usage:**

The `RegExp` object is used in the "RegExp" test case. A regular expression (or RegExp) is a string that defines a search pattern for a specific sequence of characters.

**Special JS feature or syntax:**

No special JavaScript features or syntax are explicitly mentioned, but it's worth noting that these methods are all part of the standard JavaScript API and don't rely on any advanced or experimental features.

**Other alternatives:**

Some alternative approaches to check if a string starts with a specific character could include:

* Using the `startsWith` method in combination with another library like Lodash
* Utilizing a custom implementation using bitwise operations (e.g., checking the first byte of the string)
* Leveraging other libraries or frameworks that provide optimized string manipulation functions.

However, these alternatives might not be as straightforward or readable as the methods compared in this benchmark.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36

Browser/OS: Chrome 76 on Mac OS X 10.11.6

View result in a separate tab

Test name	Executions per second
index	3941149.5 Ops/sec
charAt()	3878599.5 Ops/sec
startsWith()	3931649.5 Ops/sec
slice()	3594637.5 Ops/sec
RegExp	3180349.5 Ops/sec

Related benchmarks:

String test comparison (version: 0)

Test various way of testing a string starts with a specific character

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

Created: 5 years ago by: Registered User

Jump to the latest result

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 27 days ago):