Run results for: Replace with regex or replace

Run details:

User agent: Mozilla/5.0 (Linux; arm_64; Android 12; M2101K6G) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.5112.114 YaBrowser/22.9.4.79.00 SA/3 Mobile Safari/537.36

Browser: Yandex Browser 22

Operating system: Android

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
regex	452483.3 Ops/sec
replace	961190.1 Ops/sec

Script Preparation code:

var css = `@charset "UTF-8";

.dx-validationsummary-item-content {
  border-bottom: 1px dashed;
  display: inline-block;
  line-height: normal;
}
@-webkit-keyframes valid-badge-frames {
  from {
    opacity: 0;
    -webkit-transform: scale(.1);
    transform: scale(.1);
  }
  to {
    opacity: 1;
    -webkit-transform: scale(1);
    transform: scale(1);
  }
}`;

var header = '/** created by devexpress \n version: 1.1.1\n copyright\n*/';
var result = '';

Tests:

regex
result = css.replace(/^(@charset "UTF-8";\n)?([\S\s]*)/, `$1${header}$2`);
replace
if (css.startsWith('@charset "UTF-8";')) { result = `@charset "UTF-8";\n${header}${css.replace('@charset "UTF-8";\n', '')}`; } else { result = header + css; }