let str = "Lower And Upper";
let lower = str.toLowerCase();
//lower is "lower and upper"
let upper = str.toUpperCase();
//upper is "LOWER AND UPPER"
let capitalize = getCapitalize(str);
//capitalize is "Lower and upper"
console.log(`lower is \"${lower}\"`);
console.log(`upper is \"${upper}\"`);
console.log(`capitalize is \"${capitalize}\"`);
function getCapitalize(word) {
if (!word) return word;
return word[0].toUpperCase() +
word.substring(1).toLowerCase();
}