CallBySharing.js

//this function is a 'side-effects' function: it doesn't return anything, it just changes the values passed in 
function changeStuff(num, obj1, obj2){
  //remember that parameters are implicit variable declarations; these three parameters
  //are variables local to this function 
  num = num * 10;
  obj1.item = "changed";
  obj2 = {item: "changed"};
}

var num = 10;
var obj1 = {item: "unchanged"};
var obj2 = {item: "unchanged"};

changeStuff(num, obj1, obj2);

console.log(num);           //  10
console.log(obj1.item);     // 'changed'
console.log(obj2.item);     // 'unchanged'


//EXAMPLE 2: 
function f(a,b,c) {
   a = 3;
   b.push("foo");
   c.first = false;
}

var x = 4;
var y = ["eeny", "miny", "mo"];
var z = {first: true};

f(x,y,z);

console.log(x)      // 4
console.log(y)      // ["eeny", "miny", "mo", "foo"]
console.log(z)      // {first: false}