Benchmark: padStart vs splice vs loop

Tests:

padStart
let x = 5; let res = ("" + x).padStart(6, "0")
splice
let x = 5; let res = ("0000000" + x).slice(-6)
loop
let x = 5; let res = ''+x while (res.length < 6) { res = '0' + res; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
padStart
splice
loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
padStart	11226049.0 Ops/sec
splice	64921824.0 Ops/sec
loop	10264284.0 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 its components.

**Benchmark Overview**

The benchmark measures the performance of three different approaches to pad or manipulate strings in JavaScript:

1. `padStart`: Using the `padStart` method to add leading zeros to a string.
2. `splice`: Using the `splice` method to insert one or more characters at a specified position in a string.
3. A custom "loop" approach, where a while loop is used to concatenate zeros to the end of a string.

**Library Used**

None of the test cases use any external libraries.

**Special JS Features/Syntax**

The benchmark uses some special JavaScript features and syntax:

* The `padStart` method was introduced in ECMAScript 2017.
* The `slice` method was introduced in ECMAScript 2009. However, it's not a string manipulation method like `padStart`, but rather a general-purpose array method that can be used with strings.

**Benchmark Approach**

The benchmark approach consists of three test cases:

1. **`padStart`**: This test case creates an empty string and pads it with leading zeros using the `padStart` method.
2. **`splice`**: This test case creates an empty string and inserts six zeros at the beginning using the `splice` method (specifically, `-6` as the index).
3. **`loop`**: This test case creates an empty string and concatenates zeros to it in a while loop until its length reaches 6.

**Comparison**

The benchmark compares the performance of these three approaches:

* `padStart`: Uses the `padStart` method, which is likely to be faster since it's optimized for this specific use case.
* `splice`: Uses the `splice` method, which may incur additional overhead due to its general-purpose nature and string manipulation requirements.
* `loop`: Uses a custom while loop approach, which may have performance characteristics similar to `padStart`, but with more overhead due to the explicit looping.

**Pros and Cons**

Here are some pros and cons of each approach:

* **`padStart`**:
	+ Pros: Optimized for string padding, likely faster execution.
	+ Cons: Requires ECMAScript 2017 support.
* **`splice`**:
	+ Pros: General-purpose method with multiple uses.
	+ Cons: May incur additional overhead due to string manipulation requirements.
* **`loop`**:
	+ Pros: Custom implementation may be optimized for specific use cases.
	+ Cons: Requires explicit looping, which can lead to performance overhead.

**Other Alternatives**

Some alternative approaches could have been considered:

* Using the `repeat` method (ECMAScript 2015) instead of concatenation in the `loop` test case.
* Using a library like Lodash or String-pooling to optimize string manipulation performance.
* Experimenting with other string padding methods, such as using `String.fromCharCode` and `Array.prototype.fill`.

Keep in mind that these alternatives may not provide significant benefits over the current implementation, and may require additional testing and optimization to achieve noticeable improvements.

Related benchmarks:

padStart vs splice vs loop (version: 0)

Measures speed between using padStart and splice and a pad loop

Comparing performance of: padStart vs splice vs loop

Created: 3 years ago by: Guest

Jump to the latest result

padStart

splice

loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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