Benchmark: isUpperCase - MeasureThat.net

Tests:

char code
var isUpperCase = c => 'A' <= c && c <= 'Z'; for(c = 0; c < 128; c++) { isUpperCase(String.fromCharCode(c)); }
regex
var isUpperCase = c => /[A-Z]/.test(c); for(c = 0; c < 128; c++) { isUpperCase(String.fromCharCode(c)); }
toLowerCase
var isUpperCase = c => c !== c.toLowerCase(); for(c = 0; c < 128; c++) { isUpperCase(String.fromCharCode(c)); }
char code 2
var isUpperCase = c => { d = c.charCodeAt(); return 64 < d && d < 91; } for(c = 0; c < 128; c++) { isUpperCase(String.fromCharCode(c)); }

Rendered benchmark preparation results:

Previous results

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Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36

Browser/OS: Chrome 92 on Windows

isUpperCase (version: 0)