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How do I use the setItem(), getItem(), and removeItem() methods to store and retrieve data in localStorage and sessionStorage?
How do I use the setItem(), getItem(), and removeItem() methods to store and retrieve data in localStorage and sessionStorage?
Jun 24, 2025 am 12:51 AM
The difference between localStorage and sessionStorage is data persistence. 1.localStorage is used for long-term storage, and the data remains after closing the browser; 2.sessionStorage is only valid during the current session, and clears when closing the page or window. Both store data through setItem(), getItem() gets the data, removeItem() deletes the data, and use JSON.stringify() to convert the object when storing it, and use JSON.parse to restore it when obtaining it.
When working with client-side storage in JavaScript, localStorage and sessionStorage are two of the most commonly used APIs. They allow you to store data directly in the user's browser using simple key-value pairs. To interact with them, you'll mainly use three methods: setItem() , getItem() , and removeItem() .
Here's how they work and when to use each one.
Storing Data with setItem()
The setItem() method is used to save data into either localStorage or sessionStorage . It takes two parameters: a key (as a string) and a value (also as a string).
localStorage.setItem('username', 'john_doe'); sessionStorage.setItem('theme', 'dark');
A few things to note:
If the key already exists,
setItem()will overwrite the existing value.Only strings can be stored directly. If you want to store an object or array, you need to convert it to a JSON string first:
const user = { name: 'Alice', age: 30 }; localStorage.setItem('user', JSON.stringify(user));
This is important because trying to store non-string values ??directly will result in unexpected behavior.
Retrieving Data with getItem()
Once data is stored, you can retrieve it using the getItem() method by passing in the key.
const username = localStorage.getItem('username'); console.log(username); // Outputs: john_doe
If the key doesn't exist, getItem() returns null . So it's a good idea to check for that before trying to use the value.
Also, if you stored an object or array using JSON.stringify() , don't forget to parse it back:
const userData = localStorage.getItem('user'); const user = userData ? JSON.parse(userData) : null;
This ensures that your data remains usable as a JavaScript object.
Removing Data with removeItem()
If you no longer need a particular piece of data, use removeItem() to delete it by key:
localStorage.removeItem('username'); sessionStorage.removeItem('theme');
It's important to know that this only removes the item you specify — it won't clear everything unless you call it for every key individually or use clear() .
Choosing Between localStorage and sessionStorage
While both storage types use the same methods, their behavior differences:
-
localStoragepersists even after the browser is closed and reopened. -
sessionStorageonly lasts for the duration of the page session — closing the tab or window clears it.
So if you're storing something temporary like form state during a single visit, go with sessionStorage . For long-term storage like user preferences, use localStorage .
That's basically how these methods work. The trickiest part is remembering to convert objects and handle return values ??properly — but once you get the hang of it, it's straightforward.
The above is the detailed content of How do I use the setItem(), getItem(), and removeItem() methods to store and retrieve data in localStorage and sessionStorage?. For more information, please follow other related articles on the PHP Chinese website!
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