ProperCase.js

/**
 *  Adding a new case converter called Proper case
 *  Proper case is also called Pascal case 
 *  Where every word begins with an upper case
 *  All the remaiing letters of the words are lower
 */

function convertToProper(...words) {

    // Proper case is also called PascalCase
    // Every word starts with an upper letter
    // All the remaining letters are lower

    let result = "";

    // Go thru every word
    for (word of words) {

        // First letter is upper
        result += word
            .slice(0, 1)
            .toUpperCase();
            
        // Rest all are lower
        result += word
            .slice(1)
            .toLowerCase();
        }
    } 
    return result;
}