js check capital letter code example

Example 1: javascript check if all capital letter

function isUpper(str) {
    return !/[a-z]/.test(str) && /[A-Z]/.test(str);
}

isUpper("FOO"); //true
isUpper("bar"); //false
isUpper("123"); //false
isUpper("123a"); //false
isUpper("123A"); //true
isUpper("A123"); //true
isUpper(""); //false

Example 2: capitalize in javascript

const name = 'flavio'
const nameCapitalized = name.charAt(0).toUpperCase() + name.slice(1)

Example 3: check if letter is uppercase javascript

isUpperCase('A') // true
isUpperCase('a') // false