React Fundamentals: Components, Props, State, and Hooks

React becomes much easier once you understand a few core ideas: components, props, state, events, and Hooks.

1. Components: The Building Blocks of a React App

A component is a reusable piece of UI.

Instead of building an entire page inside one large file, you can split the interface into smaller components.

For example, a job website might have:

Each component has a specific responsibility.

A simple component can look like this:

You can then use it inside another component:

The benefit becomes obvious as an application grows. Instead of maintaining one huge component, you can divide the interface into smaller pieces that are easier to understand and reuse.

A practical rule

Create a separate component when a piece of UI has its own responsibility, needs to be reused, or has become difficult to manage inside its parent.

Don't split every few lines into a component just for the sake of splitting it.

2. JSX: Describing the UI

React commonly uses JSX to describe what should appear on the screen.

For example:

The expression inside {} allows JavaScript values and expressions to be used inside JSX.

For example:

JSX may look like HTML, but it is used inside JavaScript code and can be combined with JavaScript logic.

This becomes especially useful when the UI depends on application data.

3. Props: Passing Data Between Components

Props allow a parent component to pass information to a child component.

Consider a reusable job card:

The parent component can provide the values:

The basic flow is:

Parent component → props → child component

Props make components reusable because the same component can display different data.

For example, a single JobCard component can represent hundreds of different jobs on a job platform.

4. State: Data That Changes Over Time

Props are passed into a component. State is information that a component needs to remember and update.

Common examples include:

• Search text
• Selected filters
• Modal visibility
• Form input
• Counter values
• Selected jobs
• Loading status

React provides useState for managing this type of data.

When the button is clicked, the state changes and React updates the UI.

The important idea is:

State changes → React updates the UI

You generally should not manually manipulate the DOM to update UI that React is managing.

5. Events: Making the UI Interactive

React applications need to respond to user actions.

For example:

Common React event handlers include:

• onClick
• onChange
• onSubmit
• onFocus
• onBlur

A search box can combine events with state:

Now React controls the value of the input.

This pattern is common in search interfaces, filters, forms, dashboards, and admin panels.

6. Rendering Lists with map()

Most real applications display collections of data.

For example:

You can render the jobs using map():

The key helps React identify individual items in the list.

Use a stable identifier when possible:

rather than generating a random value every time the component renders.

7. Conditional Rendering

Applications often need to display different UI depending on the current state.

For example:

You can also use && when something should only appear when a condition is true:

Conditional rendering is useful for:

• Loading states
• Empty states
• Authentication
• Admin controls
• Error messages
• Feature visibility

8. Forms: A Common React Pattern

Forms are one of the most common places where React state is used.

The flow is straightforward:

1. The input value is stored in state.
2. onChange updates the state.
3. onSubmit handles submission.
4. preventDefault() prevents the browser's default form submission.

The same pattern can be expanded into registration forms, job application forms, profile editors, and admin forms.

9. Hooks: Adding React Features to Components

Hooks are functions that let components use React features.

Some commonly used Hooks include:

Start with useState and useEffect before trying to learn every Hook at once.

For example:

Here, the state stores the jobs while the Effect synchronizes the component with the API request.

Do not put every piece of logic inside useEffect. First ask whether the logic actually needs to synchronize with something outside React.

10. Keep State Simple

One common beginner mistake is storing information that can already be calculated from existing data.

For example, this can create unnecessary state:

If fullName can be calculated from existing values, you usually don't need another state variable.

Instead:

Keeping state minimal makes components easier to understand and maintain.

When multiple components need the same changing information, consider moving the state to their closest common parent or using an appropriate shared-state solution.

11. A Practical React Project Structure

As a project grows, organization becomes important.

A simple React application might look like:

The exact folder structure is not a React requirement.

The important thing is keeping responsibilities clear.

For example:

• components → reusable UI
• pages → larger screens
• hooks → reusable React logic
• services → API and external-service logic
• assets → static files

As the application grows, you can also organize code around features instead of keeping everything in one global folder structure.

12. Common React Mistakes Beginners Make

Mutating State Directly

Avoid changing state objects directly:

Instead, create a new value and update state through the setter.

Calling Hooks Conditionally

Avoid:

Hooks should be called at the top level of a component or another Hook.

Creating One Giant Component

A component that handles hundreds of lines of unrelated UI and logic can become difficult to maintain.

Split responsibilities when it makes the code easier to understand.

Using State for Everything

Not every value needs to be state.

Ask:

Does changing this value need to cause the UI to update?

If not, state may not be necessary.

Ignoring JavaScript Fundamentals

React does not replace JavaScript.

You should be comfortable with:

• Functions
• Arrays
• Objects
• Destructuring
• map()
• filter()
• find()
• Promises
• async/await
• Modules
• Modern JavaScript syntax

13. Build Something Instead of Only Watching Tutorials

The best way to understand React is to use it in projects.

A practical progression is:

The projects should become progressively more realistic. For example, a job-search application can combine several React concepts:

• Components for job cards
• Props for job information
• State for filters
• Events for search
• Lists for job results
• Conditional rendering for empty states
• Forms for applications
• API calls for backend data
• Reusable Hooks for shared logic This gives you experience solving actual UI problems instead of only reproducing tutorial code.

14. A Job-Ready React Checklist

Before moving into advanced React development, make sure you can explain and implement:

• Components
• JSX
• Props
• State
• Event handling
• Conditional rendering
• List rendering
• Forms
• useState
• useEffect
• useContext
• useReducer
• useRef
• Custom Hooks
• API integration
• Loading and error states
• Component composition
• Reusable components
• Basic performance concepts More importantly, you should be able to explain why you chose a particular approach. That matters during technical interviews because interviewers often ask about the decisions behind your implementation, not just whether you know the syntax.

15. What to Build for a React Portfolio

If your goal is a frontend developer role, build projects that demonstrate different skills.

Project 1: Job Search Dashboard

Include:

• Search
• Filters
• Pagination
• Job details
• API integration
• Loading states
• Empty states
• Responsive UI

Project 2: Admin Dashboard

Include:

• Authentication
• Tables
• Forms
• CRUD operations
• Charts
• Role-based UI

Project 3: Full-Stack Application

Combine React with a backend such as Node.js, Express, NestJS, or another backend technology you understand. Include:

• Authentication
• Database integration
• API calls
• Validation
• Error handling
• Deployment For Karyvio readers, these project ideas are especially relevant because they resemble interfaces developers work with in real products: job boards, dashboards, forms, search experiences, and content platforms.

16. React Learning Path

If you are starting from the beginning, don't jump directly into advanced libraries. A practical learning path is:

Once these fundamentals are comfortable, you can start exploring the wider React ecosystem based on the type of applications you want to build.

Final Takeaway

Learning React is not about memorizing every Hook or copying projects from tutorials. The important skill is understanding how data flows through components and how the UI responds when that data changes. Start with components, props, state, events, lists, and forms. Then move into Hooks and API integration. After that, build projects where you have to make your own decisions about component structure, state, data flow, and user experience. If you can start with a blank project and build a functional interface without following a tutorial line by line, you are moving from learning React toward actually using React as a developer. For job preparation, keep the cycle simple: Learn → Build → Debug → Deploy → Explain That is the foundation you can build on as you move toward production React development.

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