Benchmark: leftPadtest - MeasureThat.net

Tests:

leftpad1
function leftpad1(str, len, ch){ return (ch + str).slice(-len) }
leftpad2
function leftpad0(str, len, ch) { str = String(str); var i = -1; if (!ch && ch !== 0) ch = " "; len = len - str.length; while (++i < len) { str = ch + str; } return str; }
primeagen
function leftpad3(str, len, ch) { return new Array(len - str.length).join(!ch && ch !== 0 ? " " : ch) + str; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
leftpad1
leftpad2
primeagen

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
leftpad1	918665856.0 Ops/sec
leftpad2	990028480.0 Ops/sec
primeagen	962038912.0 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 JSON and explain what's being tested, compared, and other considerations.

**Benchmark Definition**

The benchmark definition is missing in the provided JSON. It should contain information about the test case, such as the function name, input parameters, and expected output.

**Individual Test Cases**

There are three test cases:

1. `leftpad1`
	* Benchmark Definition: This function takes a string (`str`), a length (`len`), and a character (`ch`) as inputs. It returns the left-padded string by concatenating the character to the right of the original string using the `slice()` method.
2. `leftpad0`
	* Benchmark Definition: This function is similar to `leftpad1`, but it uses a different approach:
		+ Converts the input string to a primitive value (`str = String(str)`).
		+ Initializes an index variable (`i`) and checks if the character is null or zero (`ch`).
		+ Calculates the length of padding required by subtracting the original string's length from the desired length.
		+ Loops through the padding characters, concatenating them to the left of the original string using `ch + str`.
3. `primeagen`
	* Benchmark Definition: This function is not a standard JavaScript function and appears to be unrelated to the left-padding test case.

**Comparison**

The benchmark tests different approaches for left-padding:

1. **`leftpad1`**: Uses the `slice()` method, which creates a new string by extracting a subset of characters from an existing string.
2. **`leftpad0`**: Uses a loop to concatenate padding characters to the original string.

**Pros and Cons**

* `leftpad1`:
	+ Pros: Efficient use of `slice()`, concise code.
	+ Cons: May not be suitable for large strings due to memory allocation overhead.
* `leftpad0`:
	+ Pros: More explicit control over padding, handles edge cases (null or zero character).
	+ Cons: Longer code, more verbose.

**Library**

None of the test cases use a standard JavaScript library. However, `String()` is used in `leftpad0`, which is a built-in function.

**Special JS Features/Syntax**

None of the test cases explicitly utilize special JavaScript features or syntax (e.g., async/await, arrow functions).

**Alternatives**

For left-padding, other approaches could include:

1. Using string interpolation methods like `String.prototype.padStart()` (if supported by the browser).
2. Utilizing string manipulation libraries like `lodash`.
3. Implementing a custom padding algorithm using bitwise operations or regular expressions.

In summary, the benchmark tests three different approaches for left-padding: `leftpad1` uses `slice()`, `leftpad0` uses a loop, and `primeagen` is not a standard JavaScript function. The pros and cons of each approach highlight the trade-offs between efficiency, conciseness, and explicit control in coding.

Related benchmarks:

leftPadtest (version: 0)

Comparing performance of: leftpad1 vs leftpad2 vs primeagen

Created: 2 years ago by: Guest

Jump to the latest result

leftpad1

leftpad2

primeagen

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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