Why is null stored as a string in localStorage?

Question

In the Chrome console I set foo to null:

localStorage.setItem(\"foo\",null)

Then I test, whether it is null:

Answer 1

As per spec, localstorage uses Storage object interface

interface Storage {
  readonly attribute unsigned long length;
  DOMString? key(unsigned long index);
  getter DOMString? getItem(DOMString key);
  setter void setItem(DOMString key, DOMString value); //notice this line
  deleter void removeItem(DOMString key);
  void clear();
};

setter method translates to setItem, accepts only DOMString

As per documentation

DOMString is a UTF-16 String. As JavaScript already uses such strings, DOMString is mapped directly to a String.

Passing null to a method or parameter accepting a DOMString typically stringifies to "null".