Void Type - void

The void type represents a value that is nothing and may only be void or undefined.

This is usually used for functions to hint they have no return. Otherwise, this data type is practically useless, as it is practically only a synonym for undefined.

The only difference is that void is indicating that the value is always nothing, while undefined is indicating that the value is nothing at the moment but may be something later (Like in an optional parameter or a variable that is not yet assigned).

This also means comparing void to undefined will always be true:

var var1: void = void;
var var2: undefined = undefined;

var1 == var2; // true

Note that unlike in JavaScript, void is not an operator, but a type. This means that standard syntax of void 0 is not valid in this language. Instead, simply use void.

Examples

Creating a void variable

var var1: void = void;

Using void to indicate a function has no return

def func1() -> void {
  return;
}

Explicitly returning void for a function

def func2() -> void {
  return void;
}

Assigning void value to a void variable

var var23: void = func2();

X Can not assign to a void variable anything but void

// X May not set a 'void' variable to anything except 'void'
var var2: void = 4;