SSR vs CSR mental model in Vue - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding SSR and CSR rendering timing

In Vue with SSR and CSR, when does the initial HTML content become visible to the user?

A SSR sends fully rendered HTML from the server immediately; CSR renders HTML only after JavaScript loads in the browser.

B CSR sends fully rendered HTML from the server immediately; SSR renders HTML only after JavaScript loads in the browser.

C Both SSR and CSR send empty HTML and rely on JavaScript to render content after loading.

D SSR and CSR both send fully rendered HTML from the server immediately.

💡 Hint

Think about which process happens on the server and which happens on the client.

SSR (Server-Side Rendering) generates the full HTML on the server and sends it to the browser, so users see content immediately. CSR (Client-Side Rendering) sends minimal HTML and relies on JavaScript running in the browser to build the page, causing a delay before content appears.

❓ component_behavior

intermediate

Vue component hydration in SSR

After Vue SSR sends HTML to the browser, what does hydration do?

A Hydration disables JavaScript to improve performance.

B Hydration reloads the entire page to fetch fresh data from the server.

C Hydration attaches Vue's event listeners and makes the static HTML interactive without re-rendering the entire page.

D Hydration removes the server-rendered HTML and replaces it with a blank page.

💡 Hint

Hydration connects static HTML with Vue's dynamic features.

Hydration is the process where Vue takes the server-rendered HTML and attaches event listeners and reactive behavior so the page becomes interactive without rebuilding the whole DOM.

❓ state_output

advanced

State availability in SSR vs CSR

Consider a Vue app that fetches user data asynchronously. Which statement best describes when the user data is available in SSR vs CSR?

A Both SSR and CSR include user data in the HTML before sending.

B In CSR, user data is fetched and included in the HTML before sending; in SSR, data is fetched after the page loads in the browser.

C Both SSR and CSR fetch user data only after the page loads in the browser.

D In SSR, user data is fetched and included in the HTML before sending; in CSR, data is fetched after the page loads in the browser.

💡 Hint

Think about where the data fetching happens in SSR vs CSR.

SSR fetches data on the server and includes it in the HTML sent to the client, so the page is ready with data immediately. CSR fetches data only after the JavaScript runs in the browser, causing a delay before data appears.

📝 Syntax

advanced

Detecting SSR-only code in Vue

Which Vue code snippet correctly runs only during SSR and not in the browser?

Vue

export default {
  setup() {
    if (typeof window === 'undefined') {
      console.log('Running on server')
    }
  }
}

A if (typeof window !== 'undefined') { console.log('Running on server') }

B if (typeof window === 'undefined') { console.log('Running on server') }

C if (window === null) { console.log('Running on server') }

D if (window) { console.log('Running on server') }

💡 Hint

Check how to detect server environment in JavaScript.

On the server, the window object does not exist, so typeof window === 'undefined' is true only during SSR.

❓ lifecycle

expert

Vue lifecycle differences in SSR vs CSR

Which Vue lifecycle hook runs only on the client side and never during SSR?

A onMounted

B setup

C beforeCreate

D created

💡 Hint

Think about when the DOM is available.

onMounted runs after the component is mounted to the DOM, which only happens in the browser. SSR does not mount components to a DOM, so onMounted never runs during SSR.

Practice

1. What does SSR (Server-Side Rendering) mean in Vue applications?

easy

A. The server builds the full HTML page before sending it to the browser.

B. The browser builds the page after loading JavaScript.

C. The page is built only when the user clicks a button.

D. The server sends only data, and the browser builds the page.

Solution

1. Step 1: Understand SSR concept

   SSR means the server prepares the full HTML content before sending it to the browser.

2. Step 2: Compare with other options

   The options describing browser building the page after loading JavaScript and server sending only data describe CSR behavior, while the button-click option is unrelated to SSR.

3. Final Answer:

   The server builds the full HTML page before sending it to the browser. -> Option A

4. Quick Check:

   SSR = Server builds page first [OK]

Hint: SSR means server sends ready HTML, not just data [OK]

Common Mistakes:

• Confusing SSR with CSR
• Thinking SSR means browser builds page
• Assuming SSR only sends data, not HTML

2. Which Vue code snippet correctly represents a CSR approach?

easy

A. fetch('/api/data').then(res => res.json())

B. export default { ssr: true, setup() { return {} } }

C. const app = Vue.createSSRApp({ template: 'Hello' })

D. const app = Vue.createApp({ data() { return { count: 0 } } }).mount('#app')

Solution

1. Step 1: Identify CSR code pattern

   CSR uses Vue.createApp() to mount app in browser after loading.

2. Step 2: Check other options

   export default { ssr: true, setup() { return {} } } mentions SSR flag, C uses SSR app creation, A is just data fetching.

3. Final Answer:

   const app = Vue.createApp({ data() { return { count: 0 } } }).mount('#app') -> Option D

4. Quick Check:

   CSR uses createApp and mounts in browser [OK]

Hint: CSR uses createApp and mounts in browser [OK]

Common Mistakes:

• Confusing createApp with createSSRApp
• Thinking SSR flag means CSR
• Assuming fetch alone is CSR

3. Given a Vue app using SSR, what will the user see immediately after the server sends the page?

medium

A. The fully rendered HTML page visible instantly.

B. A blank page until JavaScript loads and runs.

C. Only a loading spinner with no content.

D. An error message about missing components.

Solution

1. Step 1: Understand SSR output

   SSR sends fully rendered HTML, so the user sees content immediately.

2. Step 2: Contrast with CSR behavior

   CSR shows blank or spinner until JS runs; SSR avoids this delay.

3. Final Answer:

   The fully rendered HTML page visible instantly. -> Option A

4. Quick Check:

   SSR = instant HTML visible [OK]

Hint: SSR shows full page immediately, no blank screen [OK]

Common Mistakes:

• Thinking SSR waits for JavaScript to load
• Confusing loading spinner with SSR
• Assuming SSR causes errors on load

4. You have a Vue SSR app, but the page stays blank after loading. What is a likely cause?

medium

A. The client-side JavaScript failed to hydrate the server HTML.

B. The server did not send any HTML content.

C. The browser does not support JavaScript.

D. The Vue app was created with createApp instead of createSSRApp.

Solution

1. Step 1: Understand SSR delivery

   In SSR, the server must send fully rendered HTML; a blank page indicates the server rendered no content or sent empty HTML.

2. Step 2: Rule out client-side issues

   Hydration failure leaves static HTML visible; no JS support shows static HTML; using createApp may cause flicker but content appears.

3. Final Answer:

   The server did not send any HTML content. -> Option B

4. Quick Check:

   Blank SSR page = no HTML from server [OK]

Hint: Blank page in SSR means server sent no HTML content [OK]

Common Mistakes:

• Thinking hydration failure causes blank (leaves static HTML)
• Blaming browser JS support (shows static without JS)
• Assuming createApp causes blank (re-renders on client)

5. You want fast initial load and good SEO for a Vue app with dynamic user data. Which approach fits best?

hard

A. Use SSR but disable hydration to speed up loading.

B. Use CSR only, loading data after page loads in browser.

C. Use SSR to render the page on the server, then hydrate on client.

D. Use CSR with server sending only JSON data.

Solution

1. Step 1: Analyze requirements

   Fast initial load and SEO need server-rendered HTML visible to search engines.

2. Step 2: Match approach to needs

   SSR renders HTML on server, improving SEO and load speed; hydration enables interactivity.

3. Step 3: Evaluate other options

   CSR delays content rendering, SSR without hydration loses interactivity, CSR with JSON only delays content.

4. Final Answer:

   Use SSR to render the page on the server, then hydrate on client. -> Option C

5. Quick Check:

   SSR + hydration = fast load + SEO + interactivity [OK]

Hint: SSR with hydration balances speed, SEO, and interactivity [OK]

Common Mistakes:

• Choosing CSR only for SEO needs
• Disabling hydration losing interactivity
• Assuming JSON data alone improves SEO