When saving values in localStorage those values are saved as string.  There are some guidelines when checking for undefined vs. null. 

Checking localStorage.variableName === undefined is the way to checked it.

Checking getItem("variableName") === null is the way to go.

Here is a sample and results in the console.

function testLocalStorage()
{
	console.log('TESTING localStorage.value1')
	if (localStorage.value1 === undefined) 
		console.log('localStorage.value1 - is undefined');

	if (localStorage.value1 === null) 
		console.log('localStorage.value1 - is null');
	
	console.log('\n');			
	console.log('TESTING getItem("value2")');

	var licValue = localStorage.getItem("value2");

	if(licValue === undefined) 
		console.log('getItem(localStorage.value2) - is undefined');

	if(licValue === null) 
		console.log('getItem(localStorage.value2) - is null');			 
}	

*** CONSOLE RESULTS ***

TESTING localStorage.value1
localStorage.value1 - is undefined

TESTING getItem("value2")
getItem(localStorage.value2) - is null