Concept of Immutable and Mutable
Immutable : We can not change value of primitive type, all the primitive types are immutable
Ex : null, undefined, string, number, boolean
1. When we do operations like below , it will return new string
var str = “abc”;
str.toLowerCase, str.split
Mutable : you can change the properties or itself the object to the some other value. You can change the property of Object or you can change the property of Arrays
Ex : Object , Arrays
