Benchmark: JS Regex vs .startsWith vs .indexOf vs. slice equals

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:

regex start
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var regex = window.regexStart; while (x < TOTAL_STRINGS) { const str = data[x]; regex.test(str); x += 1; }
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; }
regex end
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var regex = window.regexEnd; while (x < TOTAL_STRINGS) { const str = data[x]; regex.test(str); x += 1; }
endsWith
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; }
indexOf start
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.indexOf(match) === 0; x += 1; }
indexOf end
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.indexOf(match) === str.length - length; x += 1; }
slice start equals
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.slice(0, 4) === match; x += 1; }
slice end equals
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.slice(-4) === match; x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
regex start
startsWith
regex end
endsWith
indexOf start
indexOf end
slice start equals
slice end equals

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36 Edg/141.0.0.0

Browser/OS: Chrome 141 on Windows

View result in a separate tab

Test name	Executions per second
regex start	647.8 Ops/sec
startsWith	1371.9 Ops/sec
regex end	582.1 Ops/sec
endsWith	1378.4 Ops/sec
indexOf start	15233.9 Ops/sec
indexOf end	15436.2 Ops/sec
slice start equals	1056.5 Ops/sec
slice end equals	1086.3 Ops/sec

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

LLMs can make mistakes. Check important info.

**What is tested?**

The benchmark measures the performance of different string comparison methods in JavaScript:

1. `indexOf`: finds the index of the first occurrence of a substring within another string.
2. `slice`: extracts a portion of a string.
3. String equality using `===` (including `startsWith`, `endsWith`, and `localeCompare`).

**Comparison methods**

The benchmark compares the performance of each method across various browsers, devices, and operating systems.

**Key findings**

1. The order of operations matters: `slice` is faster than `indexOf`, which is faster than string equality using `===`.
2. Browser differences are significant: Firefox 129 performs better on some tests, while other browsers (e.g., Chrome) may outperform it.
3. Device platform and operating system have an impact: desktop vs. mobile devices, and Windows vs. other OSes.

**Performance comparison**

Here's a rough ranking of the methods by performance:

1. `slice` (start or end)
2. `indexOf`
3. String equality using `===`

The order may vary depending on specific test cases and browser versions.

**Code implications**

These results suggest that developers should use `slice` for string comparisons when possible, as it is generally the fastest method. However, if a specific use case requires `indexOf` or string equality using `===`, those methods can be used instead.

The performance differences between browsers and devices highlight the importance of optimizing code for specific platforms and versions.

Related benchmarks:

JS Regex vs .startsWith vs .indexOf vs. slice equals (version: 0)

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

Comparing performance of: regex start vs startsWith vs regex end vs endsWith vs indexOf start vs indexOf end vs slice start equals vs slice end equals

Created: 5 years ago by: Guest

Jump to the latest result

regex start

startsWith

regex end

endsWith

indexOf start

indexOf end

slice start equals

slice end equals

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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