Benchmark: padStart vs slice

Tests:

padStart
let x = "5"; let res = x.padStart(2, "0")
splice
let x = "5"; let res = ("0" + x).slice(-2)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
padStart
splice

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36 Edg/138.0.0.0

Browser/OS: Chrome 138 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
padStart	65069220.0 Ops/sec
splice	139782816.0 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 JSON and explain what's being tested, compared, and the pros and cons of different approaches.

**Benchmark Definition**

The benchmark measures the speed between two string manipulation methods: `padStart` and `slice`. The test case uses a variable-length string (`"5"`), which will be padded with zeros to a fixed length (in this case, 2).

**Options being compared**

There are two options being compared:

1. **padStart**: This method pads the string on the left with characters specified by the `padChar` parameter.
2. **slice**: This method extracts a section of a string and returns it.

**Pros and Cons**

### padStart

Pros:

* More efficient when you need to pad on the left side, as it avoids creating an intermediate string.
* Can be more readable, especially when used with fixed lengths or specific padding characters.

Cons:

* Requires two arguments (the length to pad to and the padding character), which can lead to confusion if not used correctly.
* Not all browsers support `padStart` (it was introduced in ECMAScript 2017).

### slice

Pros:

* Widely supported across different browsers and versions.
* Only requires a single argument (the number of characters to extract).
* Can be more flexible, as you can use negative numbers or zero to start extracting from the end.

Cons:

* Creates an intermediate string, which can lead to increased memory allocation and garbage collection overhead.
* Less readable than `padStart`, especially when dealing with variable-length padding.

**Library/Language features**

There is no library involved in this benchmark. However, it's worth noting that both methods are standardized in ECMAScript (JavaScript), ensuring consistency across different browsers and versions.

**Special JS feature/syntax**

This benchmark does not use any special JavaScript features or syntax that would require additional explanation.

**Other alternatives**

If you needed to pad a string with zeros without using the `padStart` method, other alternatives could include:

1. Using concatenation: `"0".repeat(2) + x`
2. Using the `padEnd` method (also introduced in ECMAScript 2017): `x.padEnd(2, "0")`

However, these approaches are generally less efficient and more prone to errors than using `padStart`.

Related benchmarks:

padStart vs slice (version: 0)

Measures speed between using padStart and slice

Comparing performance of: padStart vs splice

Created: 3 years ago by: Guest

Jump to the latest result

padStart

splice

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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