Run results for: startsWith vs slice vs substring

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 YaBrowser/23.7.1.1215 Yowser/2.5 Safari/537.36

Browser: Yandex Browser 23

Operating system: Linux

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
JS startsWith	3686.5 Ops/sec
JS slice	3703.4 Ops/sec
JS substring	3484.8 Ops/sec

Script Preparation code:

window.prefix = "%%SOME_PREFIX%%";
const possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

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;
}

window.allStrings = [];
for (let i = 0; i < 1000; i++) {
	allStrings.push(window.prefix + makeRandomString(1000));
	allStrings.push(makeRandomString(1000));
}

Tests:

JS startsWith
window.allStrings.forEach(s => { s.startsWith(window.prefix); })
JS slice
let len = window.prefix.length; window.allStrings.forEach(s => { s.slice(0, len) === window.prefix; })
JS substring
let len = window.prefix.length; window.allStrings.forEach(s => { s.substring(0, len) === window.prefix; })

Run results for: startsWith vs slice vs substring

JS startsWith

JS slice

JS substring