Reusable UI components in React - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple reusable button component in React.

React

function Button({ label }) {
  return <button>[1];</button>;
}

Drag options to blanks, or click blank then click option'

Acontent

Btext

Clabel

Dchildren

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong prop name like 'text' or 'children' which are not defined here.

The label prop is used to display the button text inside the button element.

2fill in blank

medium

Complete the code to pass a click handler to the reusable button component.

React

function Button({ label, [1] }) {
  return <button onClick={handleClick}>{label}</button>;
}

Drag options to blanks, or click blank then click option'

AonClick

BclickHandler

ChandleClick

DonPress

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-standard prop names like 'clickHandler' or 'onPress' which React does not recognize.

The prop onClick is the standard React event handler for button clicks.

3fill in blank

hard

Fix the error in the reusable button component to correctly call the click handler passed as a prop.

React

function Button({ label, onClick }) {
  return <button onClick=[1]>{label}</button>;
}

Drag options to blanks, or click blank then click option'

AonClick

BonClick()

ChandleClick

DonClick => onClick()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the function immediately with parentheses, which triggers it on render.

You should pass the function reference onClick directly, not call it immediately.

4fill in blank

hard

Fill both blanks to create a reusable input component that updates its value on change.

React

function TextInput({ value, [1] }) {
  return <input type="text" value={value} onChange=[2] />;
}

Drag options to blanks, or click blank then click option'

AonChange

BhandleChange

CsetValue

DupdateValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect prop names or not passing the handler function properly.

The prop onChange is used to handle input changes, and handleChange is the function passed to update the value.

5fill in blank

hard

Fill all three blanks to create a reusable list component that renders items with keys.

React

function ItemList({ items }) {
  return (
    <ul>
      {items.map([1] => (
        <li key=[2]>[3]</li>
      ))}
    </ul>
  );
}

Drag options to blanks, or click blank then click option'

Aitem

Bitem.id

Citem.name

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using index as key which can cause rendering issues.

Not using the correct variable name inside the map.

We map over items using item as the variable. The key uses item.id for uniqueness, and we display item.name inside the list item.

Practice

1. What is the main benefit of creating reusable UI components in React?

easy

A. They automatically fix bugs

B. They make the app run faster

C. They save time and keep the app consistent

D. They replace the need for CSS styling

Solution

1. Step 1: Understand the purpose of reusable components

   Reusable components are designed to be used multiple times, reducing repeated code.

2. Step 2: Identify the main benefit

   Using reusable components saves development time and keeps the app's look and behavior consistent.

3. Final Answer:

   They save time and keep the app consistent -> Option C

4. Quick Check:

   Reusable components = save time + consistency [OK]

Hint: Reusable means use again to save time and stay consistent [OK]

Common Mistakes:

• Thinking reusable components speed up app runtime
• Believing they fix bugs automatically
• Confusing styling with component reuse

2. Which of the following is the correct way to pass a prop named title with value "Hello" to a React component Card?

easy

A.

B.

C.

D.

Solution

1. Step 1: Recall JSX prop syntax

   Props are passed as attributes with name=value pairs, using quotes for strings.

2. Step 2: Check each option

   uses correct JSX syntax: title="Hello". Others have syntax errors.

3. Final Answer:

   <Card title="Hello" /> -> Option A

4. Quick Check:

   Props in JSX use name="value" [OK]

Hint: Props look like HTML attributes with quotes for strings [OK]

Common Mistakes:

• Using curly braces without variable (Option B)
• Adding extra quotes around prop name (Option C)
• Using colon instead of equals (Option A)

3. Given this React component:

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

// Usage:
<Button label="Click me" />

What will be rendered on the page?

medium

A. label

B. Nothing will render

C. {label}

D. Click me

Solution

1. Step 1: Understand prop usage in the component

   The component receives label as a prop and inserts it inside the button element.

2. Step 2: Check the usage

   The component is used with label="Click me", so the button shows "Click me" text.

3. Final Answer:

   <button>Click me</button> -> Option D

4. Quick Check:

   Prop label = "Click me" shown inside button [OK]

Hint: Props passed show as content inside component tags [OK]

Common Mistakes:

• Thinking the literal word 'label' appears
• Confusing JSX expression with string
• Assuming component renders nothing without explicit return

4. What is wrong with this reusable React component code?

function Alert(props) {
  return <div>{message}</div>;
}

// Usage:
<Alert message="Warning!" />

medium

A. The variable 'message' is not defined inside the component

B. The component does not receive props correctly

C. The usage of the component is incorrect

D. The component should return a button instead of a div

Solution

1. Step 1: Check how props are used inside the component

   The component uses {message} but does not extract it from props.

2. Step 2: Identify the error

   Since message is not defined or extracted, this causes a reference error.

3. Final Answer:

   The variable 'message' is not defined inside the component -> Option A

4. Quick Check:

   Props must be accessed via props or destructuring [OK]

Hint: Always get props from function parameter before use [OK]

Common Mistakes:

• Using prop names directly without props or destructuring
• Assuming usage syntax is wrong
• Thinking component must return button

5. You want to create a reusable Input component that can show a label and accept user input. Which approach correctly allows customizing the label text and input placeholder using props?

hard

A. function Input() {
return (
<label>
label
<input placeholder="placeholder" />
</label>
);
}

B. function Input({ label, placeholder }) {
return (
<label>
{label}
<input placeholder={placeholder} />
</label>
);
}

C. function Input(props) {
return (
<label>
props.label
<input placeholder="props.placeholder" />
</label>
);
}

D. function Input({ label, placeholder }) {
return (
<label>
<input placeholder={label} />
{placeholder}
</label>
);
}

Solution

1. Step 1: Check prop usage for label and placeholder

   Props should be destructured and used inside JSX expressions with curly braces.

2. Step 2: Verify correct placement of label and placeholder

   function Input({ label, placeholder }) { return ( <label> {label} <input placeholder={placeholder} /> </label> ); } correctly places label text and uses placeholder prop inside input element.

3. Final Answer:

   function Input({ label, placeholder }) { return ( <label> {label} <input placeholder={placeholder} /> </label> ); } -> Option B

4. Quick Check:

   Destructure props and use inside JSX with curly braces [OK]

Hint: Destructure props and use inside JSX with curly braces [OK]

Common Mistakes:

• Using prop names as plain text instead of expressions
• Putting placeholder text in wrong prop
• Mixing label and placeholder positions