Run results for: .charAt vs .indexOf vs Str[idx] vs startWith

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 13_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/83.0.4103.88 Mobile/15E148 Safari/604.1

Browser: Chrome Mobile iOS 83

Operating system: iOS 13.4

Device Platform: Mobile

Date tested: 4 years ago

Test name	Executions per second
.charAt	164.6 Ops/sec
.indexOf	111.1 Ops/sec
Str[index]	356.2 Ops/sec
.startWith	207.1 Ops/sec

HTML Preparation code:

<div></div>

Script Preparation code:

window.regex = /^test/;
window.match = '9';
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:

.charAt
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.charAt(0) === match; x += 1; }
.indexOf
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; }
Str[index]
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[0] === match; x += 1; }
.startWith
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; }

Run results for: .charAt vs .indexOf vs Str[idx] vs startWith

Testing some things

.charAt

.indexOf

Str[index]

.startWith