Why routing is needed for SPAs in Vue - Performance Evidence

Performance: Why routing is needed for SPAs

MEDIUM IMPACT

Routing in SPAs affects page load speed and interaction responsiveness by managing content changes without full page reloads.

Navigating between views in a single-page application

Vue

this.$router.push('/about');

Changes view without reloading page, preserving app state and speeding up navigation.

📈 Performance GainSingle reflow, no full page reload, interaction is near instant

Navigating between views in a single-page application

Vue

window.location.href = '/about';

Triggers a full page reload, causing slow load and losing app state.

📉 Performance CostBlocks rendering for 500-1000ms depending on network, triggers full reflow and repaint

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Full page reload on navigation	High (reloads entire DOM)	Multiple (full reflow)	High (full repaint)	[X] Bad
Client-side routing with Vue Router	Low (updates small DOM parts)	Single or none	Low (partial repaint)	[OK] Good

Rendering Pipeline

Routing updates the URL and swaps components without reloading, so the browser skips full HTML parsing and style recalculation.

→JavaScript Execution

→Layout

→Paint

→Composite

⚠️ BottleneckLayout due to DOM updates when components change

Core Web Vital Affected

INP

Routing in SPAs affects page load speed and interaction responsiveness by managing content changes without full page reloads.

Optimization Tips

1Use client-side routing to avoid full page reloads in SPAs.

2Efficient routing reduces layout thrashing and improves interaction speed.

3Monitor navigation performance with browser DevTools to catch slow reloads.

Performance Quiz - 3 Questions

What is the main performance benefit of using client-side routing in SPAs?

A Increases bundle size for faster rendering

B Avoids full page reloads, speeding up navigation

C Loads all pages at once to reduce network requests

D Triggers more reflows for better layout accuracy

DevTools: Performance

How to check: Record a navigation event, compare full page reload vs client-side route change timings.

What to look for: Look for long tasks and layout shifts during navigation; client-side routing shows shorter tasks and fewer layout shifts.

Practice

1. Why do Single Page Applications (SPAs) need routing?
Routing in SPAs helps to:

easy

A. Change views without reloading the whole page

B. Reload the entire website every time a link is clicked

C. Make the website slower by adding extra pages

D. Disable navigation between different parts of the app

Solution

1. Step 1: Understand SPA behavior

   SPAs load a single HTML page and dynamically update content without full reloads.

2. Step 2: Role of routing in SPAs

   Routing allows switching views inside the SPA without refreshing the browser, improving speed and user experience.

3. Final Answer:

   Change views without reloading the whole page -> Option A

4. Quick Check:

   Routing in SPAs = Change views without reload [OK]

Hint: Routing changes views inside SPA without page reload [OK]

Common Mistakes:

• Thinking SPAs reload the whole page on navigation
• Confusing routing with server-side page loads
• Believing routing disables navigation

2. Which of the following is the correct way to define a route in Vue Router?

easy

A. const routes = { '/home': HomePage }

B. const routes = [{ path: '/home', component: HomePage }]

C. const routes = ['/home', HomePage]

D. const routes = [path: '/home', component: HomePage]

Solution

1. Step 1: Recall Vue Router route syntax

   Routes are defined as an array of objects with path and component keys.

2. Step 2: Match syntax with options

   const routes = [{ path: '/home', component: HomePage }] correctly uses an array with an object containing path and component.

3. Final Answer:

   const routes = [{ path: '/home', component: HomePage }] -> Option B

4. Quick Check:

   Vue Router routes = array of objects with path and component [OK]

Hint: Routes are array of objects with path and component keys [OK]

Common Mistakes:

• Using object instead of array for routes
• Missing curly braces for route objects
• Incorrect array structure without keys

3. Given this Vue Router setup:

const routes = [
  { path: '/', component: Home },
  { path: '/about', component: About }
];

// User visits '/about'

What component will Vue display?

medium

A. No component, blank page

B. Home component

C. About component

D. Error message

Solution

1. Step 1: Check the route matching the URL

   The URL '/about' matches the route with path '/about' which uses the About component.

2. Step 2: Determine displayed component

   Vue Router will render the About component for the '/about' path.

3. Final Answer:

   About component -> Option C

4. Quick Check:

   URL '/about' shows About component [OK]

Hint: URL path matches route path to show component [OK]

Common Mistakes:

• Assuming default '/' route always shows
• Confusing component names
• Thinking Vue reloads page instead of switching component

4. What is wrong with this Vue Router code?

const routes = [
  { path: '/home', component: Home },
  { path: '/about', component: About }
]

const router = createRouter({
  history: createWebHistory,
  routes
})

medium

A. createWebHistory is missing parentheses

B. Routes array should be an object

C. Component names must be strings

D. Router must be created with createRouter()

Solution

1. Step 1: Check usage of createWebHistory

   createWebHistory is a function and must be called with parentheses to return history object.

2. Step 2: Identify error in code

   Code uses createWebHistory without parentheses, so history is not set correctly.

3. Final Answer:

   createWebHistory is missing parentheses -> Option A

4. Quick Check:

   Functions need () when called [OK]

Hint: Functions like createWebHistory need () to run [OK]

Common Mistakes:

• Forgetting parentheses on function calls
• Confusing array and object syntax for routes
• Thinking component names must be strings

5. You want users to bookmark and share specific views in your Vue SPA. How does routing help achieve this?

hard

A. Routing disables navigation to prevent URL changes

B. Routing reloads the page to show the bookmarked view

C. Routing hides the URL so users cannot share links

D. Routing updates the URL to reflect the current view without reloading

Solution

1. Step 1: Understand URL role in SPAs

   SPAs use routing to change the URL path dynamically without full page reloads.

2. Step 2: How routing supports bookmarking

   By updating the URL, routing lets users bookmark or share links that open the app at the same view.

3. Final Answer:

   Routing updates the URL to reflect the current view without reloading -> Option D

4. Quick Check:

   Routing updates URL for sharing/bookmarking [OK]

Hint: Routing changes URL so views can be bookmarked/shared [OK]

Common Mistakes:

• Thinking routing reloads the page for bookmarks
• Believing URLs stay static in SPAs
• Assuming routing disables URL changes