Benchmark: padStart vs slice vs string

Tests:

padStart
let x = "5"; let res = x.padStart(2, "0")
splice
let x = "5"; let res = ("0" + x).slice(-2)
string
let x = 5; let res = x < 10 ? `0${x}` : `${x}`

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
padStart
splice
string

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser/OS: Chrome 132 on Windows

View result in a separate tab

Test name	Executions per second
padStart	35881208.0 Ops/sec
splice	101823456.0 Ops/sec
string	106650968.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of what is tested on the provided JSON.

The benchmark measures the speed between three different approaches:

1. **`padStart()`**: This method pads the string with spaces on the left to reach a specified length. In this case, it's used to pad the string "5" with two zeros to make it at least 2 characters long.
2. **`slice()`**: This method extracts a section of a string and returns it as a new string. In this case, it's used to extract the last two characters of the concatenated string ("0" + x).
3. **String concatenation using template literals or implicit concatenation** (the `string` test case): This approach uses the fact that in JavaScript, you can concatenate strings by implicitly adding them together, like `"0" + x`. This is used to create a new string by prepending "0" to the value of x.

Now, let's discuss the pros and cons of each approach:

* **`padStart()`**: Pros:
	+ It's a built-in method in JavaScript, so it's likely to be optimized for performance.
	+ It's clear and concise way to pad a string.
Cons:
	+ May have additional processing overhead due to the padding process.
	+ Can be slower than implicit concatenation or `slice()` for very large strings.
* **`slice()`**: Pros:
	+ Fast and efficient, as it only requires extracting a section of the string.
	+ Can be faster than `padStart()` for very large strings.
Cons:
	+ Requires an additional function call, which can have overhead.
	+ May not be as readable or concise as `padStart()`.
* **String concatenation using template literals or implicit concatenation** (the `string` test case): Pros:
	+ Fast and efficient, as it avoids the overhead of function calls and built-in methods.
Cons:
	+ May have additional complexity due to the use of implicit concatenation or template literals.
	+ Can be less readable than other approaches.

Other considerations:

* The benchmark uses a relatively simple input string ("5") to test these approaches. For larger strings, `slice()` might still be faster, while `padStart()` could become slower due to its padding process.
* The use of implicit concatenation or template literals can lead to additional complexity and potential issues if not handled correctly.

Now, regarding the libraries used in these tests:

None. These tests only rely on built-in JavaScript methods and features.

As for special JS features or syntax, this benchmark doesn't explicitly test any specific features like async/await, promises, or ES6+ modules. However, it does use implicit concatenation, which is a more modern approach to string concatenation in JavaScript.

Finally, other alternatives could include:

* Using `repeat()` method instead of `padStart()`: This would create a new string with the specified number of repetitions of the pad character.
* Using a custom function for padding or concatenation: Depending on the specific requirements and performance considerations, it might be beneficial to implement a custom solution using a loop or recursion.

Keep in mind that these alternatives would likely have different trade-offs regarding performance, readability, and complexity.

Related benchmarks:

padStart vs slice vs string (version: 0)

Measures speed between using padStart and slice and string

Comparing performance of: padStart vs splice vs string

Created: one year ago by: Guest

Jump to the latest result

padStart

splice

string

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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