How can I check if a string is all uppercase in JavaScript?

You can compare the string against itself in upper case to check if it is in the upper case.

Example

function isUpperCase(str) {
   return str === str.toUpperCase();
}
console.log(isUpperCase('a'))
console.log(isUpperCase('A'))
console.log(isUpperCase('ASDF 123 asd'))
console.log(isUpperCase('TEST 123 TEST'))

Output

This will give the output −

false
true
false
true