- Update state based on events
- Work with multiple state variables together
In the labs for this section, we'll be working on a grocery list app. Some of this app is already built out using static versions of the components. We'll be using state and events to make our app dynamic.
The components you have to work with are in the src/components folder. Start
by examining these components and draw out your component hierarchy to see how
data can be passed from one component to another.
In this lab, you'll update state and get more practice with the useState hook.
It's recommended that you run npm start and work on this in the browser
before running tests. Try to get your app to match the demo! Once you've
built out the components below, run npm test or learn test to see if your
code passes the tests.
In the App component, there is a button for toggling between dark mode and
light mode. Using the useState hook, create a state variable in the App
component. Then, use that variable to determine if our app should be in dark
mode or light mode.
You will also need to add an event handler to the dark mode button, and update state when the button is clicked.
The actual functionality of changing our app's theme is handled in CSS, so all
you have to do is set up the code to update the className of the div based on
your state variable:
<div className="App dark">
{/* for dark mode */}
</div>
<div className="App light">
{/* for light mode */}
</div>In the Item component, when the user clicks the <button> element, the item
should be added to their virtual cart. The way we'll show the user that the item
is in the cart is by changing the className on the <li> element:
<li className="in-cart">
{/* the item is in the cart */}
</li>
<li className="">
{/* the item is NOT in the cart */}
</li>If the item is not in the cart, the <button> element's text should read "Add
to Cart", and if the item is in the cart, the <button> element's text should
read "Remove From Cart". Naturally, you'll also need to add state to the Item
component to solve this deliverable!
In the ShoppingList component, there is a <select> element that will allow
us to filter the list of items by category.
Use the useState hook to create a state variable called selectedCategory for
keeping track of the selected value from this <select> element. When the value
of the <select> element is changed, update state.
You should also use the selectedCategory variable to determine which items to
display in the shopping list. You'll need some way of filtering the array of
items based on the selectedCategory.