LocalStorage - check if key exists

Question

What's the difference between:

if (localStorage.regionCode) { }

AND

if (localStorage.getItem('regionCode') !== null) { }

The first will also "say" there is no `regionCode` if `regionCode` contains an empty string — Andreas, Jul 20 '17 at 15:41

Roman · Accepted Answer · 2017-07-20T18:07:10.310

1

In JavaScript you have truthy and falsey. This means that every condition converts in an condition-statement to a boolean and represents true or false.

Explenation

If localStorage.regionCode is an empty string if(localStorage.regionCode) would converts to false otherwise true.

For more details you could read the blog post about truthy and falsey

edited Jul 20 '17 at 18:07

answered Jul 20 '17 at 17:11

Roman

4,922
3
22
31

1

The Storage API only stores strings: https://developer.mozilla.org/en-US/docs/Web/API/Storage/setItem – Andreas Jul 20 '17 at 17:31
@Andreas thanks for your note. – Roman Jul 20 '17 at 18:08

score 0 · Answer 2 · edited Jul 20 '17 at 15:42

0

In first case it is checking if there exist any storage item with name regionCode. In this case it will be undefined if there is no key by name regionCode in localStorage & in second case it is checking the value of the localStorage key regionCode which will return null.

See the information listed here.

edited Jul 20 '17 at 15:42

SimplyComplexable

1,116
11
19

answered Jul 20 '17 at 15:39

brk

48,835
10
56
78

score 0 · Answer 3 · answered Jul 20 '17 at 15:48

0

!== null condition will be always fulfilled if only regionCode prop exists.

Similar situation with localStorage.regionCode with a slight difference, that it won't pass if regionCode is an empty string.

answered Jul 20 '17 at 15:48

kind user

40,029
7
67
77

LocalStorage - check if key exists

3 Answers3

Explenation