how to first letter capital in javascript code example

Example 1: javascript capitalize words

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

Example 2: javascript capitalize first letter

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

Example 3: js capitalize first letter of each word

const titleCase = title => title
    .split(/ /g).map(word =>
        `${word.substring(0,1).toUpperCase()}${word.substring(1)}`)
    .join(" ");