Answers for "how to change letter in upercase in javascript"

uppercase string in js

var str = "Hello World!";
var res = str.toUpperCase();  //HELLO WORLD!

capitalize in javascript

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

first letter tuUppercase

const string = "tHIS STRING'S CAPITALISATION WILL BE FIXED."
const string = string[0].toUpperCase() + string.slice(1)