The local storage functionality in browsers is a bit limited and this can lead to some rather surprising behaviour.
localStorage[0] = false;
if (localStorage[0]) {
console.log('wtf'); // runs?!
}
When checking the value stored in localStorage, it appears that the boolean
was silently converted to the string "false", which is truthy.
Turns out that this is one of those cases where it pays off to carefully read the specification, which states that local storage only accepts string values!
If you want to store an object or other type of value, you can serialize the
data with JSON.stringify and load it again with JSON.parse.
— @Overv