Object properties Inheritance

object-extending.js

function defaultStrFns(someStr) {
     let arr;
     function splitIntoArray() {
          arr = someStr.split('');
          return arr;
     }
  
     function concatFromArray() {
          return arr.join('');
     }
  
     return {
         splitIntoArray: splitIntoArray,
         concatFromArray: concatFromArray
     }
}

function extendStrFns(someStr) {
     function splitIntoArrayUsingComa() {
          return someStr.split(',');
     }
  
     return {
         splitIntoArrayUsingComa: splitIntoArrayUsingComa
     }
}

function extendedStringFns(someStr) {
    return Object.assign(defaultStrFns(someStr), extendStrFns(someStr));
}