Run results for: .startsWith vs .charAt vs .charCodeAt for single character

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser: Chrome 130

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 10 days ago

Test name	Executions per second
startsWith	2718.7 Ops/sec
.charAt	1347.6 Ops/sec
charCodeAt	1462.9 Ops/sec
string[]	1385.1 Ops/sec

HTML Preparation code:

<div></div>

Script Preparation code:

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 y = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var regex = window.regex; while (x < TOTAL_STRINGS) { const str = data[x]; if (str.startsWith("A")) y += x; x += 1; }
.charAt
var x = 0; var y = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; if (str.charAt(0) === 'A') y += x; x += 1; }
charCodeAt
var x = 0; var y = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; if (str.charCodeAt(0) === 65) y += x; x += 1; }
string[]
var x = 0; var y = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; if (str[0] === 'A') y += x; x += 1; }

Run results for: .startsWith vs .charAt vs .charCodeAt for single character

Testing some things

startsWith

.charAt

charCodeAt

string[]