Benchmark: startsWith vs substring vs indexOf

Tests:

startsWith
let s_test = '0x101010'; if (s_test.startsWith('0x')) s_test = s_test.slice(2);
substring
let s_test = '0x101010'; if (s_test.substring(0, 2) === "0x") s_test = s_test.slice(2);
indexOf
let s_test = '0x101010'; if (s_test.indexOf("0x") === 0) s_test = s_test.slice(2);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
substring
indexOf

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36

Browser/OS: Chrome 96 on Windows

View result in a separate tab

Test name	Executions per second
startsWith	60213756.0 Ops/sec
substring	66706704.0 Ops/sec
indexOf	719735872.0 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case that compares the performance of three different methods to check if a string starts with a specific prefix: `startsWith`, `substring`, and `indexOf`. Let's break down what each option is, its pros and cons, and other considerations.

**Option 1: `startsWith`**

The `startsWith` method checks if the string starts with the specified prefix. It does this by comparing the substring of the original string starting from the beginning to the specified length (`length`) against the prefix.

Pros:

* Simple and efficient implementation
* Works well for most use cases

Cons:

* Can be slower than other methods when dealing with very long strings, as it involves a loop to check each character
* Not suitable for non-ASCII characters, where the comparison may not work as expected

Other considerations:

* `startsWith` is implemented in WebKit-based browsers (Chrome, Safari), but not in Firefox or Edge. This might affect the benchmark results.

**Option 2: `substring`**

The `substring` method returns a new string that starts at the specified index and has a specified length. It can be used to check if the original string starts with a prefix by comparing the resulting substring against the prefix.

Pros:

* Can be faster than `startsWith` for very long strings, as it avoids loop-based comparisons
* Works well for non-ASCII characters

Cons:

* More complex implementation compared to `startsWith`
* May introduce additional overhead due to string creation and comparison

**Option 3: `indexOf`**

The `indexOf` method returns the index of the specified value within the string. If the value is not found, it returns -1. This method can be used to check if the original string starts with a prefix by checking if the index returned by `indexOf` is greater than or equal to 0.

Pros:

* Can be faster than `startsWith` for very long strings, as it avoids loop-based comparisons
* Works well for non-ASCII characters

Cons:

* More complex implementation compared to `startsWith`
* May introduce additional overhead due to string searching and comparison

**Library usage**

In the provided benchmark test case, none of the options explicitly use any JavaScript libraries. However, in real-world scenarios, you might encounter situations where one or more of these methods are used within a library or framework.

For example, in the `startsWith` method, it's possible that some libraries may provide an optimized implementation for this specific operation. In such cases, using the library-provided implementation might result in better performance.

**Special JavaScript features and syntax**

The provided benchmark test case does not use any special JavaScript features or syntax beyond what is standard in JavaScript. However, if you were to modify the code to take advantage of modern JavaScript features like `const`, `let`, `Arrow functions`, or async/await, it might affect the performance results.

In summary:

* `startsWith` and `indexOf` are suitable for most use cases due to their simplicity and efficiency.
* `substring` is a good alternative when dealing with very long strings or non-ASCII characters.
* The choice of method ultimately depends on the specific requirements and constraints of your project.
* Be mindful of potential differences in implementation between WebKit-based browsers (Chrome, Safari) and non-WEBkit browsers (Firefox, Edge).
* Modern JavaScript features might affect performance results if not used carefully.

**Other alternatives**

If you're looking for alternative methods to check if a string starts with a specific prefix, you could consider:

* Using `regex` patterns: You can use regular expressions to match the prefix at the start of the string. This method is more flexible and powerful but may be slower due to the overhead of regex matching.
* Implementing a custom string searching algorithm: Depending on your specific requirements, you might be able to implement an optimized string searching algorithm that outperforms the built-in methods.

In conclusion, understanding the trade-offs between `startsWith`, `substring`, and `indexOf` will help you make informed decisions when choosing a method for your JavaScript projects.

Related benchmarks:

startsWith vs substring vs indexOf (version: 0)

startsWith vs substring vs indexOf

Comparing performance of: startsWith vs substring vs indexOf

Created: 3 years ago by: Registered User

Jump to the latest result

startsWith

substring

indexOf

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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