Benchmark: JS Regex vs .startsWith vs .indexOf Jan

HTML Preparation code:

<div></div>

Script Preparation code:

window.regexpStart = new RegExp('^p.*', 'i');
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.regexpStart; 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); 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.toLowerCase().indexOf(match) === 0; x += 1; }
toLowerCase().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.toLowerCase().startsWith(match); x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
regex start
startsWith
indexOf start
toLowerCase().startsWith

Fastest: N/A

Slowest: N/A

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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/93.0.4577.82 Safari/537.36

Browser/OS: Chrome 93 on Windows

View result in a separate tab

Test name	Executions per second
regex start	531.4 Ops/sec
startsWith	634.8 Ops/sec
indexOf start	10898.2 Ops/sec
toLowerCase().startsWith	326.5 Ops/sec

JS Regex vs .startsWith vs .indexOf Jan (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 indexOf start vs toLowerCase().startsWith

Created: 2 years ago by: Guest

Jump to the latest result

regex start

startsWith

indexOf start

toLowerCase().startsWith

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A