JavaScript Mutable and Immutable Objects

In JavaScript Primitives are immutable, which means that the value is passed instead of reference.
For Objects the reference is passed instead of value. Example as below,

//Primitives are immutable

var a = 10;

var b = a;

console.log("a: "+a);

console.log("b: "+b);

a =20;

console.log("a: "+a);

console.log("b: "+b);

//Mutable

var c = {name: "Zack"};

var d = c;

console.log("c: "+c.name);

console.log("d: "+d.name);

d.name = "Arnold";

console.log("c: "+c.name);

console.log("d: "+d.name);

Ensure whether you are passing value or reference during development. This is one of the basic concepts in JavaScript.