javascript is pass by value

javascript primitive varialbles are passed by value to a function. Objects are also passed by value but the difference is that the value of the reference of the object is passed to a function. The snippet below, the value of the references of b and c are passed into the function. Within the function, the change to the b is changing the internal value of the object, thus the change will be visible to all other references that is pointing to this object. The changes to the c is changing the value of reference itself by creating a brand new object, so the value of the reference is pointing to a new object, the old object stays the same.

function doUpdate(a, b, c)
  a = a * 2;
  b.msg = "hey";
  c = {msg: "hey"};

var num = 10;
var obj1 = {msg: "greetings"};
var obj2 = {msg: "greetings"};

doUpdate(num, obj1, obj2);

console.log(num);		// 10
console.log(obj1.msg);	// hey    
console.log(obj2.msg);	// greetings

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