Michelle Garrett

Difference between var and val in Scala

scala

var and val can both be used to define values in Scala, but differ when it comes to mutability. Generally val is preferred, as it better aligns with the functional programming style.

var #

var represents a variable. It is a mutable reference to a value, meaning its value can change. It can be reassigned with another value of the same type. Similar to var or let in JavaScript.

  var x = 123 // defines variable x, of type Int

  x = 321 // x can be redefined to 321, since it's a var
  x = "hello" // x cannot be redefined to a string, since x is of type Int

val #

val represents a value. It is immutable, meaning its value never changes. It cannot be reassigned with a different value. Similar to const in JavaScript.

  val x = 123 // defines value x, of type Int

  x = 321 // x cannot be redefined to 321, since it's a val