Session Plan

Forms / Event Handling

DOM Event Handlers in React

• Setting event handlers directly onto elements (e.g. onClick instead of element.addEventListener("click", …))
• Overview of event handlers exposed by React

Managing Forms

• Adding a form and adding inputs to the form
• Submitting forms with onSubmit
• Performing input validation in JavaScript (in addition to HTML input validation, and server-side input validation)

Hooks

Introduction to Hooks

• You already know one hook! -> useState
• Rules of Hooks (don't wrap in if statements, use dependency array)
• Hooks run on every render, unless they have dependencies
• Hooks run when dependencies change

How to use useEffect

• Usage of useEffect
• Dependencies of useEffect
• Use useEffect for synchronization (with external systems)
• Returning a cleanup function from useEffect

Loading Data

Connecting to APIs

• Calling async APIs using fetch, within useEffect
• Implementing initial data loading, showing a spinner

Exercises

Handling User Input & Events

1. Create a ClickCounter component

1. Create a new component called ClickCounter
2. Use the useState hook to manage a count state variable
3. Implement an onClick event handler function that increments the count
4. Render a button and display the current value of count

2. Build a SimpleForm component

1. Create a new component called SimpleForm
2. Use the useState hook to manage the state of form inputs
3. Create input fields for the form (e.g., name, email, message)
4. Implement a handleSubmit function to handle form submission
5. Render the form inputs and a submit button

3. Develop a TodoList component

1. Create a new component called TodoList
2. Use the useState hook to manage an array of todo items
3. Implement a function to add a new todo item to the array
4. Implement a function to remove a todo item from the array
5. Render a list of todo items using the .map method, ensuring each item has a unique key prop
6. Render an input field to add new todos and buttons/functionality to remove todos

Practice Using useEffect

4. Create a Clock component

1. Create a new component called Clock
2. Use the useState hook to manage the current time
3. Use the useEffect hook to set up an Interval that updates the time every second
4. Implement the cleanup function in useEffect to clear the interval when the component unmounts
5. Let the component render the current time

5. Build a DataFetcher component

1. Create a new component called DataFetcher
2. Use the useState hook to manage the data, loading, and error states
3. Use the useEffect hook to fetch data from a public API when the component mounts
4. Implement loading and error states in the component's JSX
5. Render the fetched data when it's available

6. Develop a WindowResizer component

1. Create a new component called WindowResizer
2. Use the useState hook to manage the window size
3. Use the useEffect hook to set up an event listener for the resize event
4. Update the window size state whenever the resize event is triggered
5. Implement the cleanup function in useEffect to remove the event listener when the component unmounts
6. Render the current window size in the component