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Before diving into the tutorial, it may be unclear why you’d want to even use Local Storage in your React apps.
There’s plenty of reasons and use cases, more than I can imagine, but here’s a few I’ve discovered.
App.js with the code below. Here, we’re setting up a simple to-do list app. Absolutely nothing fancy, but it’ll do the trick for playing with
After copying over this code, you should be able to add to-do items to the list and remove them.
Saving the value of our
newItem input to
localStorage is a piece of cake.
Here’s our new
As you can see, it’s not much different from updating React
Open up the Web Developer tools in your browser of choice, find the section for Web Storage (“Application” tab in Chrome), select the current domain of
localhost:3000 and watch the value for the
newItem key stay in sync with your app’s input.
When adding an item, we save the new, updated
localStorage and reset the
newItem input to a blank string.
localStorage can only store strings, arrays and objects need to be passed into
JSON.stringify() before being passed to
Before moving on, we’ll also want to update the list in
localStorage when deleting an item.
App reverts back to its initial state! We aren’t using the stored items yet, just saving them in the background. Not terribly helpful…
In order to persist the app’s
state even after refreshing the page, we need to hydrate the
App‘s state with the values in
localStorage, with help from a couple new methods:
The below method hydrates the app’s state with the values saved to
localStorage. Add this new method to your
Once you’ve added the above code to your
App component, refreshing the page no longer resets the app, but keeps it in sync with
While our app works as-is by saving React
localStorage every time the user makes an update, we don’t really need to save so frequently.
Why? Because React keeps track of the
state of the app throughout the user’s session — that’s what it’s for! Also, with more complex components and states, it’ll be quite cumbersome and repetitive to use
localStorage.setItem() wherever the
state is updated.
So rather than continuously keeping
localStorage in-sync with React
state, let’s simply save
localStorage whenever the user ends their session, either by leaving the app (‘unmounting’ the component) or refreshing the page.
Alright, here’s a new method for saving all of
localStorage at once. Add it to your
In order to save
localStorage when the user leaves the app, we need to invoke the
saveStateToLocalStorage method in
Here’s some updated code, where we add the event listener to
componentDidMount as well as add what we need to
We no longer need to
setItem when updating React
state, so you’ll want to remove those.
A lot has changed since the beginning of the tutorial, so here’s the
App.js file at this point. *Nothing in the
render() method has changed.*
And that’s it! You now have the tools to use Local Storage in your React projects.
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