Firefox wins 4 of 5 operations
Geomean of speed relative to the fastest browser per op — 1.00× = always fastest (lower is better)
Compares building a string with += concatenation against Array.prototype.join for assembling many pieces.
Firefox
Chrome
Safari
Microsoft EdgeString.prototype.startsWith performance
FirefoxChromeSafariMicrosoft EdgeCompares String.prototype.indexOf against String.prototype.includes for substring searches.
SafariFirefoxChromeMicrosoft EdgeCompares a classic indexed for loop against Array.prototype.forEach for summing an array.
FirefoxSafariChromeMicrosoft EdgeCompares String.prototype.startsWith against an anchored regular expression for prefix matching.
FirefoxSafariChromeMicrosoft Edge