step2-7.js

'use strict';

const x = 9;
function f1(val) {
  val = val + 1;
  return val;
}

f1(x);

console.log(x);

const y = { x: 9 };
function f2(val) {
  val.x = val.x + 1;
  return val;
}

f2(y);

console.log(y);

/* In the x-code, we are logging the value of x, which has not changed. If we want this code to return 10, 
we need to console.log(f1(x)).  In the y-code, y is an object. The properties of an object can be altered this way, 
so the function changes the value of x to 10. No alteration has been done to the variable reference itself. If f2 
attempted to change the *value* of y (rather than an attribute of its object), it would yield results like the x-code. 
For example, if the function is altered, val = { x: 10 }; return val;, it will return { x: 9 } */