CSS-in-JS considerations in NextJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the styled function from the styled-components library.

NextJS

import [1] from 'styled-components';

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

Astyles

Bstyle

Ccss

Dstyled

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'style' instead of 'styled' causes an import error.

Using 'css' imports a helper but not the main styled function.

The styled function is the correct import to create styled components in CSS-in-JS using styled-components.

2fill in blank

medium

Complete the code to create a styled button component with a background color of blue.

NextJS

const Button = styled.button`background-color: [1];`;

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

Ablue

Bred

Cgreen

Dyellow

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a different color than blue.

Leaving the color value empty.

The background color should be set to 'blue' as requested.

3fill in blank

hard

Fix the error in the styled component syntax by completing the missing template literal marker.

NextJS

const Container = styled.div[1]background: white; padding: 1rem;`;

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

A'

B`

C"

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Using single or double quotes instead of backticks.

Omitting the template literal marker causes syntax errors.

The styled component syntax requires a backtick ` to start the template literal.

4fill in blank

hard

Fill both blanks to correctly apply dynamic props for background and font color in a styled component.

NextJS

const Text = styled.p`background: [1]; color: [2];`;

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

Aprops => props.bgColor

Bprops => props.fontColor

Cprops => props.color

Dprops => props.background

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up background and font color props.

Using incorrect prop names that don't exist.

The background uses props.bgColor and the font color uses props.fontColor to dynamically style the component.

5fill in blank

hard

Fill all three blanks to create a styled component that changes color on hover using props.

NextJS

const Link = styled.a`color: [1]; text-decoration: none; &:hover { color: [2]; cursor: [3]; }`;

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

Aprops => props.color

Bprops => props.hoverColor

C'pointer'

D'default'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong prop names for colors.

Setting cursor to 'default' instead of 'pointer' on hover.

The link color uses props.color, changes to props.hoverColor on hover, and the cursor changes to 'pointer' to indicate it's clickable.

Practice

1. What is a key benefit of using CSS-in-JS in Next.js projects?

easy

A. CSS files load faster than inline styles.

B. It requires no JavaScript knowledge to write styles.

C. It disables server-side rendering automatically.

D. Styles are scoped to components, avoiding global conflicts.

Solution

1. Step 1: Understand CSS-in-JS scope

   CSS-in-JS keeps styles inside components, so styles don't leak globally.

2. Step 2: Compare options

   Options A, B, and D are incorrect because CSS-in-JS requires JavaScript, does not guarantee faster loading than CSS files, and does not disable server-side rendering.

3. Final Answer:

   Styles are scoped to components, avoiding global conflicts. -> Option D

4. Quick Check:

   CSS-in-JS scope = C [OK]

Hint: Remember CSS-in-JS scopes styles to components [OK]

Common Mistakes:

• Thinking CSS-in-JS disables server-side rendering
• Assuming CSS-in-JS needs no JavaScript knowledge
• Believing CSS-in-JS always loads styles faster than CSS files

2. Which of the following is the correct way to define a styled component using the styled-components library in Next.js?

easy

A. const Button = styled.button`background: blue; color: white;`;

B. const Button = styled('button') { background: blue; color: white; };

C. const Button = styled.button({ background: 'blue', color: 'white' });

D. const Button = styled.button = 'background: blue; color: white;';

Solution

1. Step 1: Recall styled-components syntax

   The correct syntax uses tagged template literals: styled.element`styles`.

2. Step 2: Check each option

   const Button = styled.button`background: blue; color: white;`; matches the correct syntax. Options A, B, and C have syntax errors or wrong usage.

3. Final Answer:

   const Button = styled.button`background: blue; color: white;`; -> Option A

4. Quick Check:

   styled-components syntax = D [OK]

Hint: Use backticks with styled.element for styles [OK]

Common Mistakes:

• Using parentheses instead of backticks
• Trying to assign styles as strings without template literals
• Confusing object syntax with styled-components tagged templates

3. Given this Next.js component using styled-jsx:

export default function Box() {
  return (
    <>
      
Hello
      
    </>
  );
}

What color will the text "Hello" appear in the browser?

medium

A. Blue

B. Red

C. Black (default)

D. Green

Solution

1. Step 1: Understand styled-jsx behavior

   styled-jsx applies scoped CSS styles to the component's elements.

2. Step 2: Check the style rule

   The style sets .box color to red, so the div with className "box" will have red text.

3. Final Answer:

   Red -> Option B

4. Quick Check:

   styled-jsx scoped style color = A [OK]

Hint: styled-jsx styles apply only inside component [OK]

Common Mistakes:

• Assuming styles apply globally
• Ignoring className matching
• Confusing default browser text color

4. You wrote this Next.js component using styled-components:

import styled from 'styled-components';

const Title = styled.h1`color: blue;`;

export default function Page() {
  return Hello World;
}

But the text color is not blue in the browser. What is the most likely cause?

medium

A. You forgot to install the styled-components package.

B. You did not wrap your app with ThemeProvider.

C. You did not add the babel-plugin-styled-components for SSR support.

D. You forgot to import React in the component.

Solution

1. Step 1: Identify styled-components SSR issue

   Without babel-plugin-styled-components, styles may not render correctly on server-side in Next.js.

2. Step 2: Check other options

   Options A and D cause errors, not silent style failure. You did not wrap your app with ThemeProvider. is optional for theming, not required for basic styles.

3. Final Answer:

   You did not add the babel-plugin-styled-components for SSR support. -> Option C

4. Quick Check:

   SSR plugin missing = B [OK]

Hint: Add babel-plugin-styled-components for SSR styles [OK]

Common Mistakes:

• Assuming ThemeProvider is required for basic styles
• Forgetting SSR plugin causes silent style issues
• Thinking missing React import causes style failure

5. You want to create a Next.js component that changes its background color based on a prop using styled-components. Which code snippet correctly implements this dynamic styling?

hard

A. const Box = styled.div`background: ${props => props.bgColor};`;

export default function ColoredBox() {
return Hi;
}

B. const Box = styled.div`background: props.bgColor;`;

export default function ColoredBox() {
return Hi;
}

C. const Box = styled.div({ background: props.bgColor });

export default function ColoredBox() {
return Hi;
}

D. const Box = styled.div`background: bgColor;`;

export default function ColoredBox() {
return Hi;
}

Solution

1. Step 1: Understand dynamic props in styled-components

   Use a function inside template literals to access props: ${props => props.propName}.

2. Step 2: Check each option

   const Box = styled.div`background: ${props => props.bgColor};`; export default function ColoredBox() { return Hi; } correctly uses the function syntax. Options B, C, and D misuse props or syntax.

3. Final Answer:

   const Box = styled.div`background: ${props => props.bgColor};`; export default function ColoredBox() { return Hi; } -> Option A

4. Quick Check:

   Dynamic props in styled-components = A [OK]

Hint: Use ${props => props.value} for dynamic styles [OK]

Common Mistakes:

• Writing props.bgColor directly inside template literal
• Using object syntax without function for props
• Forgetting to use arrow function for dynamic values