Check if a key exists in localStorage
Last updated: October 12, 2022.
If you want to retrieve something from localStorage, it is often a good idea to check if it exists first.
You can do this by checking if the return value of
localStorage.getItem('key-to-check') is equal to
localStorage.setItem('item', 'value'); console.log(localStorage.getItem('item') !== null); // Logs true console.log(localStorage.getItem('non-existent-item') !== null); // Logs false
The nice aspect to this solution is that even if an attempt is made to set the value associated with a key to
null, it is coerced to string format (
null is only returned in the absence of an item in localStorage, even if an attempt has been made to set its value to
localStorage.setItem('item', null); console.log(typeof localStorage.getItem('item')); // String // Checks type of data for the key 'item' console.log(localStorage.getItem('item') === null); // Logs false because value is not actually null... console.log(localStorage.getItem('item') === 'null'); // ...but 'null'!
The same solution also works for sessionStorage, which works in the same way but clears its contents after a user's site session.