null

undefined In Javascript undefined (a primitive type in Javascript) gets assigned to a variable that we declare but don’t assign a value to. It’s Javascript’s way of telling that the value of this variable is not defined. Even a function in Javascript which does not return anything, will return undefined by default. So, to avoid any error we should never assign undefined to a variable manually. typeof undefined; outputs: undefined; null Unlike undefined, null (another primitive type in Javascript) is used when we want to manually or intentionally set the value of a variable to be empty.