Run results for: JavaScript Case Insensitive String Start: regex vs startsWith() vs indexOf() vs localeCompare()

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36

Browser: Chrome 103

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
Regex	309.5 Ops/sec
startsWith()	48.6 Ops/sec
indexOf()	45.1 Ops/sec
localeCompare()	1.3 Ops/sec

HTML Preparation code:

<div id=''></div>

Script Preparation code:

window.target = 'tEsT';
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 outside loop
var regex = new RegExp('^'+window.target,'i'); window.data.forEach(str => regex.test(str));
startsWith()
window.data.forEach(str => str.toLowerCase().startsWith(window.target.toLowerCase()));
indexOf()
window.data.forEach(str => str.toLowerCase().indexOf(window.target.toLowerCase()) === 0);
localeCompare()
window.data.forEach(str => { str.subStr(0,window.target.length).localeCompare(window.target, undefined, { sensitivity: 'base', usage:'search'}); });
Regex inside loop
window.data.forEach(str => { (new RegExp('^'+window.target,'i')).test(str); });

Run results for: JavaScript Case Insensitive String Start: regex vs startsWith() vs indexOf() vs localeCompare()

Regex outside loop

startsWith()

indexOf()

localeCompare()

Regex inside loop