Benchmark: Check first and last char charAt startsWith slice regex.test

Script Preparation code:

var pat = "/^http.?:\/\/.+\.com/";

Tests:

index
pat[0] === "/" && pat[pat.length - 1] === "/"
charAt
pat.charAt(0) === "/" && pat.charAt(pat.length - 1) === "/"
startsWith & endsWith
pat.startsWith("/") && pat.endsWith("/")
slice
pat.slice(0, 1) === "/" && pat.slice(-1) === "/"
regex test
(/^\/.+\/$/).test(pat)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
index
charAt
startsWith & endsWith
slice
regex test

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Windows

View result in a separate tab

Test name	Executions per second
index	9205743.0 Ops/sec
charAt	9420998.0 Ops/sec
startsWith & endsWith	14483555.0 Ops/sec
slice	13918265.0 Ops/sec
regex test	19152800.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark measures the performance of different JavaScript methods to test if a string starts with or ends with a specific pattern. The pattern is defined in the "Script Preparation Code" as `var pat = "/^http.?:\\/\\/.+\\.com/";`, which matches URLs that start with `http` or `https`.

**Options being compared**

There are five options being compared:

1. **charAt**: Uses the `charAt()` method to check if the first and last characters of the string match.
2. **index**: Uses the index-based access to check if the first and last characters of the string match.
3. **slice**: Uses the `slice()` method to extract a substring from the original string, effectively checking if the first and last characters match.
4. **startsWith & endsWith**: Uses the `startsWith()` and `endsWith()` methods in combination to check if both conditions are true.
5. **regex test**: Uses a regular expression to match the pattern.

**Pros and Cons of each approach**

1. **charAt**:
	* Pros: Simple and straightforward, efficient for small strings.
	* Cons: May be slower due to the overhead of method calls and potential string concatenation issues.
2. **index**:
	* Pros: Fast and efficient, as it uses direct access to character indices.
	* Cons: May not work correctly for negative or large index values, potentially leading to errors.
3. **slice**:
	* Pros: Efficient, as it avoids creating a new string by extracting the first/last characters directly from the original string.
	* Cons: Creates a new substring, which may incur additional memory allocation and copy overhead.
4. **startsWith & endsWith**:
	* Pros: Easy to read and maintain, accurate results.
	* Cons: May be slower than other methods due to the overhead of method calls and potential string concatenation issues.
5. **regex test**:
	* Pros: Highly accurate and flexible, as it can match a wide range of patterns.
	* Cons: Slower due to the overhead of regular expression compilation and execution.

**Library and purpose**

The `^` character is used in the regex pattern to match the start of the string. The `\+` character matches one or more occurrences of any character. The `.*` part of the pattern matches any characters (including none) until the end of the string, which ensures that only URLs starting with `http` or `https` are matched.

**Special JS feature**

No special JavaScript features or syntax are used in this benchmark. However, note that some browsers may have specific optimizations or behaviors for certain methods that could affect performance.

**Other alternatives**

Some alternative approaches to testing the first and last characters of a string include:

1. **Using `substr()`**: Instead of `charAt()` or indexing directly, you can use `substr()` to extract the first/last characters.
2. **Using a temporary variable**: You can assign the first character to a temporary variable and then check if it matches another variable holding the last character.

It's worth noting that this benchmark is designed to measure the performance of specific JavaScript methods for testing string patterns, rather than providing an exhaustive comparison of all possible approaches.

Related benchmarks:

Check first and last char charAt startsWith slice regex.test (version: 0)

Comparing performance of: index vs charAt vs startsWith & endsWith vs slice vs regex test

Created: 2 years ago by: Guest

Jump to the latest result

index

charAt

startsWith & endsWith

slice

regex test

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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