mutable-vs-immutable.md

Mutable

Mutable is a type of variable that can be changed.

Immutable

Immutables are the objects whose state cannot be changed once the object is created.

If an item is mutable, modifying the copy also modifies the original.

example,

  var arr1 = [1, 2, 3]
  var arr2 = arr1
  
  arr2.push(4)
  
  console.log(arr1) // [1, 2, 3, 4]

If it’s immutable, modifying the copy does not affect the original.

example

var a = 1
var b = a
b = b + 1
console.log(a) // 1 a is same