capitalize a string javascript

1//capitalize only the first letter of the string. 
2function capitalizeFirstLetter(string) {
3    return string.charAt(0).toUpperCase() + string.slice(1);
4}
5//capitalize all words of a string. 
6function capitalizeWords(string) {
7    return string.replace(/(?:^|\s)\S/g, function(a) { return a.toUpperCase(); });
8};

1var str = "Hello World!";
2var res = str.toUpperCase();  //HELLO WORLD!

1const lower = 'this is an entirely lowercase string';
2const upper = lower.charAt(0).toUpperCase() + lower.substring(1);

1const name = 'flavio'
2const nameCapitalized = name.charAt(0).toUpperCase() + name.slice(1)
3

1const toCapitalCase = (string) => {
2    return string.charAt(0).toUpperCase() + string.slice(1);
3};

1const Capitalize = function(string){
2  return string[0].toUpperCase + string.slice(1).toLowerCase;
3}