Creating Immutable Objects:
   Here are the following ways in which you can create immutable objects:
   a) Object.assign : for creating immutable object
   b) concat: for creating immutable array
   c) filter: The filter() method creates an array filled with all array elements that pass a test (provided as a function).
             var ages = [32, 33, 16, 40];
             function checkAdult(age) {
             return age >= 18;
                      }
           function myFunction() {
           document.getElementById("demo").innerHTML = ages.filter(checkAdult);
                      }
   d) map : The map() method creates a new array with the results of calling a function for every array element.
            The map() method calls the provided function once for each element in an array, in order
   e) reduce :  The reduce() method reduces the array to a single value.
               Syntax : array.reduce(function(total, currentValue, currentIndex, arr), initialValue)