Benchmark: JS startsWith vs split

HTML Preparation code:

<div></div>

Script Preparation code:

window.regexStart = /^test/;
window.regexEnd = /test$/;
window.match = 'test';
window.matchLength = window.match.length;
var data = window.data = [];
const possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var TOTAL_STRINGS = window.TOTAL_STRINGS = 100000;

function getRandomInt(max) {
  return Math.floor(Math.random() * max);
}

function makeRandomString(len) {
  var text = "";
  for( var i=0; i < len; i++ ) {
    text += possible.charAt(getRandomInt(possible.length));
  }
  return text;
}

while (data.length < TOTAL_STRINGS) {
  data.push(makeRandomString(getRandomInt(20)));
}

Tests:

startsWith
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; str.startsWith(match) === 0; x += 1; }
split
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; var length = window.matchLength; while (x < TOTAL_STRINGS) { const str = data[x]; str.split["-"] === match; x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
split

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 11 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
startsWith	845.0 Ops/sec
split	13408.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

**Overview**

This benchmark is comparing the performance of two string manipulation methods: `startsWith` and `split`. The test case generates a large dataset of random strings and checks which method is faster to execute.

**Benchmark Definition JSON**

The benchmark definition defines two test cases:

1. "startsWith"
2. "split"

Each test case has its own script preparation code, which sets up the variables and data needed for the test.
```json
"Script Preparation Code": "window.regexStart = /^test/;\r\nwindow.regexEnd = /test$/;\r\nwindow.match = 'test';\r\nwindow.matchLength = window.match.length;\r\nvar data = window.data = [];\r\nconst possible = \"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\";\r\nvar TOTAL_STRINGS = window.TOTAL_STRINGS = 100000;\r\n"
```
The script preparation code defines two regular expressions: `regexStart` and `regexEnd`. It also sets up an array of random strings (`data`) and a variable `match`.

**Individual Test Cases**

Each test case has its own benchmark definition:
```json
{
    "Benchmark Definition": "var x = 0;\r\nvar TOTAL_STRINGS = window.TOTAL_STRINGS;\r\nvar data = window.data;\r\nvar match = window.match;\r\nwhile (x < TOTAL_STRINGS) {\r\n  const str = data[x];\r\n  str.startsWith(match) === 0;\r\n  x += 1;\r\n}",
    "Test Name": "startsWith"
}
```

```json
{
    "Benchmark Definition": "var x = 0;\r\nvar TOTAL_STRINGS = window.TOTAL_STRINGS;\r\nvar data = window.data;\r\nvar match = window.match;\r\nvar length = window.matchLength;\r\nwhile (x < TOTAL_STRINGS) {\r\n  const str = data[x];\r\n  str.split[\"-\"] === match;\r\n  x += 1;\r\n}",
    "Test Name": "split"
}
```
Each test case uses the `window` object to access the variables and data defined in the script preparation code. The test cases are executed a large number of times (defined by the `TOTAL_STRINGS` variable).

**Library and Special JS Features**

The benchmark uses two libraries:

1. **None**: The benchmark does not use any external libraries.
2. **Math.random()**: The benchmark uses the `Math.random()` function to generate random numbers.

There are no special JavaScript features or syntax used in this benchmark.

**Pros and Cons of Approaches**

Here's a brief overview of the two approaches being compared:

1. **startsWith**
	* Pros:
		+ More efficient for matching strings that start with a specific pattern.
		+ Can be optimized using regular expressions.
	* Cons:
		+ May not work as expected if the string is null or undefined.
2. **split**
	* Pros:
		+ Works well for splitting strings into substrings using a delimiter.
		+ Can be used to split strings at specific positions.
	* Cons:
		+ May not be as efficient as `startsWith` for matching strings that start with a specific pattern.

**Other Alternatives**

Other alternatives to the `startsWith` and `split` methods include:

1. **Substr**: Instead of using `split`, you could use `substr` to extract substrings from a string.
2. **IndexOf**: Another method for finding the position of a substring within a string is `indexOf`.
3. **Regexp.test**: You could also use the `test()` method of regular expressions to match strings against a pattern.

These alternatives may have different performance characteristics and use cases, depending on the specific requirements of your application.

Related benchmarks:

JS startsWith vs split (version: 0)

fork of https://www.measurethat.net/Benchmarks/Show/975/11/regex-vs-indexof-vs-startswith-vs-substr

Comparing performance of: startsWith vs split

Created: 3 years ago by: Guest

Jump to the latest result

startsWith

split

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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