How to check if a character is uppercase in JavaScript?

character === character.toUpperCase() will be true if character is uppercase.

In this example isUppercase is true:

const character = "A";
const isUppercase = character === character.toUpperCase();

In this one it is false:

const character = "a";
const isUppercase = character === character.toUpperCase();

Same code can be used to check if the whole string is uppercase:

const character = "HELLO";
const isUppercase = character === character.toUpperCase();

Finally, you can check if a single character of a longer string is uppercase with charAt:

const string = "Hello World!";

// true
if (string.charAt(0) === string.charAt(0).toUpperCase()) {
  console.log("This will be logged");
}

// false
if (string.charAt(1) === string.charAt(1).toUpperCase()) {
  console.log("This won't be logged");
}