Objects are always treated as a reference, primitives as a value. To say they're immutable requires a bit more of a context - immutable in what sense? You can r

Objects are always treated as a reference, primitives as a value. To say they're immutable requires a bit more of a context - immutable in what sense? You can reassign a different value to a variable that stores a primitive, so it's not like variables that store them are immutable. I guess that the simpliest explanation would be by code: let x = 4 let z = x z = w // x is still 4 let x = { b: 3 } let z = x z.b = 2 // x is { b: 2 }, because x and z hold reference to the same object