Using props in JSX in React - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are props in React?

Props are inputs to React components. They are like function arguments and let you pass data from a parent component to a child component.

beginner

How do you access props inside a functional component?

You receive props as a parameter in the function and access them using dot notation, like props.name.

beginner

What is the JSX syntax to use a prop called title inside a component?

You use curly braces to embed JavaScript expressions: {props.title} inside the JSX.

intermediate

Can props be changed inside a component?

No, props are read-only. You cannot modify them inside the component. To change data, use state or pass new props from the parent.

beginner

How do you pass a string prop called color with value blue to a component Box?

You write: <Box color="blue" />. This passes the string 'blue' as the color prop.

How do you pass data from a parent to a child component in React?

A Using local variables

B Using state inside the child

C Using CSS

D Using props

Props are the way to send data from parent to child components in React.

Inside a functional component, how do you access a prop named 'message'?

A props.message

B this.message

C state.message

D message()

Props are accessed via the props object, like props.message.

What is the correct JSX syntax to display a prop called 'name' inside a component?

A <props.name>

B {props.name}

C "props.name"

D (props.name)

Curly braces embed JavaScript expressions in JSX, so {props.name} shows the prop value.

Can you modify props inside a React component?

A Yes, props can be changed anytime

B Only if you use setState

C No, props are read-only

D Only in class components

Props are immutable inside components to keep data flow predictable.

How do you pass a number prop 'age' with value 30 to a component <User>?

A <User age={30} />

B <User age="30" />

C <User age='30' />

D <User age=(30) />

Use curly braces to pass numbers as props: .

Explain how props work in React and how you use them inside a functional component.

Think about how you give information to a child component.

Describe why props are read-only and what you do if you want to change data inside a component.

Consider data flow and component responsibility.

Practice

1. What is the main purpose of props in React components?

easy

A. To handle user events like clicks

B. To store internal state within a component

C. To style components with CSS

D. To pass data from a parent component to a child component

Solution

1. Step 1: Understand the role of props

   Props are used to send data from a parent component to a child component in React.

2. Step 2: Differentiate props from other concepts

   State stores internal data, events handle user actions, and CSS styles components, but props specifically pass data down.

3. Final Answer:

   To pass data from a parent component to a child component -> Option D

4. Quick Check:

   Props = Data passing [OK]

Hint: Props always send data from parent to child [OK]

Common Mistakes:

• Confusing props with state
• Thinking props handle events
• Believing props style components

2. Which of the following is the correct way to use a prop named title inside JSX?

easy

A. <h1>title</h1>

B. <h1>{title}</h1>

C. <h1>{props.title}</h1>

D. <h1>$title</h1>

Solution

1. Step 1: Use curly braces to embed prop values in JSX

   In JSX, to show a prop value, you wrap the prop access in curly braces like {props.title}.

2. Step 2: Understand context of prop usage

   The props object is passed to the component function, so access via {props.title}. Using {title} requires destructuring like function Comp({title}).

3. Final Answer:

   <h1>{props.title}</h1> -> Option C

4. Quick Check:

   Curly braces show prop values [OK]

Hint: Use curly braces { } to show props in JSX [OK]

Common Mistakes:

• Writing prop name as plain text without braces
• Using $ sign like in other languages
• Using {title} without destructuring the props object

3. Given the component:

function Greeting(props) {
  return <h2>Hello, {props.name}!</h2>;
}

// Usage:
<Greeting name="Alice" />

What will be rendered on the screen?

medium

A. Hello, {name}!

B. Hello, Alice!

C. Hello, props.name!

D. SyntaxError

Solution

1. Step 1: Identify how props are passed and used

   The Greeting component receives a prop called name with value "Alice".

2. Step 2: Understand JSX rendering with props

   The JSX uses {props.name} which inserts the string "Alice" inside the <h2> tag.

3. Final Answer:

   <h2>Hello, Alice!</h2> -> Option B

4. Quick Check:

   props.name = Alice [OK]

Hint: Props values appear inside curly braces in JSX output [OK]

Common Mistakes:

• Expecting literal text {name} instead of value
• Confusing props.name with string 'props.name'
• Thinking this causes syntax error

4. What is wrong with this React component code?

function Welcome(props) {
  return <h1>Welcome, props.name!</h1>;
}

medium

A. props.name should be inside curly braces to render its value

B. Function name should be lowercase

C. Missing return statement

D. JSX tags must be self-closing

Solution

1. Step 1: Check how props are used inside JSX

   The code writes props.name as plain text inside JSX, so it will render literally instead of the prop value.

2. Step 2: Correct usage of props in JSX

   To show the value of props.name, it must be wrapped in curly braces like {props.name}.

3. Final Answer:

   props.name should be inside curly braces to render its value -> Option A

4. Quick Check:

   Use {props.name} to show prop value [OK]

Hint: Always wrap props in { } inside JSX [OK]

Common Mistakes:

• Writing props.name as plain text
• Thinking function names must be lowercase
• Confusing JSX self-closing rules

5. You want to create a reusable Button component that shows different text based on a label prop. Which code correctly uses props to achieve this?

function Button(props) {
  return <button>???</button>;
}

Choose the correct replacement for ???.

hard

A. {props.label}

B. {label}

C. "props.label"

D. label

Solution

1. Step 1: Understand how to access props inside the component

   The component receives props as an object, so the label prop is accessed as props.label.

2. Step 2: Use curly braces to embed the prop value in JSX

   To show the value inside JSX, wrap props.label in curly braces: {props.label}.

3. Final Answer:

   {props.label} -> Option A

4. Quick Check:

   Use {props.propName} to show prop value [OK]

Hint: Use {props.propName} inside JSX to show prop values [OK]

Common Mistakes:

• Using prop name without braces
• Using braces without props object
• Using quotes around prop name