Run results for: char index vs charAt() vs slice() vs startsWith() vs RegExp -- - MeasureThat.net

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.182 Safari/537.36

Browser: Chrome 88

Operating system: Linux

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
character index	4700323.5 Ops/sec
charAt()	5020117.0 Ops/sec
startsWith()	5019167.0 Ops/sec
slice()	4330642.0 Ops/sec
RegExp	3884152.5 Ops/sec

Script Preparation code:

var str = '!foo bar baz';
var noop = Function.prototype;

Tests:

character index
if (str[0] === '!') noop();
charAt()
if (str.charAt(0) === '!') noop();
startsWith()
if (str.startsWith('!')) noop();
slice()
if (str.slice(0, 1) === '!') noop();
RegExp
const pattern = /^!/; if (pattern.test(str)) noop();