Shallow routing concept in NextJS - Mini Project: Build & Apply

Shallow Routing Concept in Next.js

📖 Scenario: You are building a simple Next.js app that shows a list of products. You want to change the URL query parameters when a user selects a product category, but you want to keep the page from fully reloading or fetching new data from the server.

🎯 Goal: Build a Next.js page that uses shallow routing to update the URL query string without triggering a full page reload or data fetch.

📋 What You'll Learn

Create a Next.js page component named ProductsPage with a list of product categories.

Add a state variable called category to track the selected category.

Use Next.js useRouter hook to update the URL query parameter category with shallow routing.

Render the selected category on the page and update the URL without full reload.

💡 Why This Matters

🌍 Real World

Shallow routing is useful in web apps where you want to update the URL to reflect UI state changes without reloading the page or fetching new data. For example, filtering products or paginating content.

💼 Career

Understanding shallow routing helps you build faster, smoother Next.js applications that improve user experience by avoiding unnecessary page reloads.

1

Setup initial product categories and state

Create a functional component called ProductsPage. Inside it, create a constant array named categories with these exact strings: 'all', 'books', 'electronics'. Also, create a state variable called category initialized to 'all' using useState.

NextJS

import { useState } from 'react';

export default function ProductsPage() {
  // Your code here
}

Hint

Use useState to create category and setCategory. Define categories as an array with the exact strings.

2

Add Next.js router and handle category change

Import useRouter from next/router. Inside ProductsPage, create a constant router by calling useRouter(). Then, write a function called handleCategoryChange that takes a parameter newCategory and calls setCategory(newCategory).

NextJS

import { useState } from 'react';
import { useRouter } from 'next/router';

export default function ProductsPage() {
  const categories = ['all', 'books', 'electronics'];
  const [category, setCategory] = useState('all');
  
  // Your code here
}

Hint

Import useRouter and call it inside the component. Define handleCategoryChange to update the state.

3

Use shallow routing to update URL query

Inside the handleCategoryChange function, after setCategory(newCategory), call router.push to update the URL with the query parameter category=newCategory. Use the current pathname from router.pathname. Pass an options object with shallow: true to enable shallow routing.

NextJS

import { useState } from 'react';
import { useRouter } from 'next/router';

export default function ProductsPage() {
  const categories = ['all', 'books', 'electronics'];
  const [category, setCategory] = useState('all');
  const router = useRouter();

  function handleCategoryChange(newCategory) {
    setCategory(newCategory);
    // Add shallow routing push here
  }
}

Hint

Use router.push with an object for pathname and query. Add { shallow: true } as the third argument.

4

Render category buttons and display selected category

In the return statement of ProductsPage, render a div containing a button for each category in categories. Each button should have an onClick handler that calls handleCategoryChange with the category string. Below the buttons, render a p element that displays the text Selected category: {category}.

NextJS

import { useState } from 'react';
import { useRouter } from 'next/router';

export default function ProductsPage() {
  const categories = ['all', 'books', 'electronics'];
  const [category, setCategory] = useState('all');
  const router = useRouter();

  function handleCategoryChange(newCategory) {
    setCategory(newCategory);
    router.push({ pathname: router.pathname, query: { category: newCategory } }, undefined, { shallow: true });
  }

  return (
    // Render buttons and selected category here
    
      {/* Your code here */}
    
  );
}

Hint

Use categories.map to create buttons. Each button calls handleCategoryChange with the category string. Show the selected category in a paragraph.

Practice

1. What does shallow routing in Next.js primarily do?

easy

A. Reloads the entire page to fetch new data

B. Prevents URL changes when navigating

C. Changes the URL without reloading the page or losing component state

D. Forces a full server-side render on every navigation

Solution

1. Step 1: Understand shallow routing purpose

   Shallow routing updates the URL but keeps the current page component and state intact without a full reload.

2. Step 2: Compare options with shallow routing behavior

   Only Changes the URL without reloading the page or losing component state describes changing the URL without reloading or losing state, matching shallow routing.

3. Final Answer:

   Changes the URL without reloading the page or losing component state -> Option C

4. Quick Check:

   Shallow routing = URL change without reload [OK]

Hint: Shallow routing changes URL but keeps page state [OK]

Common Mistakes:

• Thinking shallow routing reloads the page
• Assuming shallow routing blocks URL changes
• Confusing shallow routing with full page reload

2. Which is the correct way to enable shallow routing using Next.js router's push method?

easy

A. router.push('/page?tab=1', undefined, { shallow: true })

B. router.push('/page?tab=1', { shallow: true })

C. router.push('/page?tab=1', true)

D. router.push('/page?tab=1', { reload: false })

Solution

1. Step 1: Recall router.push syntax for shallow routing

   The third argument to router.push is an options object where shallow: true enables shallow routing.

2. Step 2: Match options with correct syntax

   router.push('/page?tab=1', undefined, { shallow: true }) correctly passes { shallow: true } as the third argument; others are incorrect or incomplete.

3. Final Answer:

   router.push('/page?tab=1', undefined, { shallow: true }) -> Option A

4. Quick Check:

   Shallow routing option is third argument object [OK]

Hint: Use third argument { shallow: true } in router.push [OK]

Common Mistakes:

• Passing shallow option as second argument
• Using boolean instead of options object
• Confusing reload option with shallow

3. Given this code snippet in a Next.js page component:

const router = useRouter();

useEffect(() => {
  console.log('Query changed:', router.query.tab);
}, [router.query.tab]);

const changeTab = () => {
  router.push('/dashboard?tab=2', undefined, { shallow: true });
};

changeTab();

What will be logged to the console after changeTab() is called?

medium

A. Query changed: 2

B. Query changed: undefined

C. Nothing is logged because shallow routing blocks query updates

D. An error occurs because shallow routing cannot update query

Solution

1. Step 1: Understand effect dependency on router.query.tab

   The effect runs when router.query.tab changes, logging its value.

2. Step 2: Analyze shallow routing effect on query

   Shallow routing updates the URL and query parameters without full reload, so router.query.tab updates to '2'.

3. Final Answer:

   Query changed: 2 -> Option A

4. Quick Check:

   Shallow routing updates query and triggers effects [OK]

Hint: Shallow routing updates query, triggers effects [OK]

Common Mistakes:

• Assuming shallow routing blocks query updates
• Expecting no console output
• Thinking shallow routing causes errors

4. Consider this Next.js code snippet:

const router = useRouter();

const handleClick = () => {
  router.push('/profile?section=info', undefined, { shallow: true });
  router.push('/profile?section=details');
};

handleClick();

What is the problem with this code regarding shallow routing?

medium

A. No problem; shallow routing applies to both pushes automatically

B. Shallow routing is ignored because it must be the first push

C. Both pushes cause full reloads because shallow routing is not supported

D. The second push overrides shallow routing, causing a full reload

Solution

1. Step 1: Examine the two router.push calls

   The first call uses shallow routing, the second does not and triggers a full reload.

2. Step 2: Understand effect of second push on routing

   The second push overrides the first and causes a full page reload, negating shallow routing.

3. Final Answer:

   The second push overrides shallow routing, causing a full reload -> Option D

4. Quick Check:

   Non-shallow push cancels shallow routing [OK]

Hint: Later push without shallow cancels shallow routing [OK]

Common Mistakes:

• Assuming shallow routing applies to all pushes automatically
• Thinking shallow routing must be first push only
• Ignoring that non-shallow push triggers reload

5. You want to implement tab navigation in a Next.js page using shallow routing to update the URL query without losing component state. Which approach correctly achieves this?

hard

A. Use router.replace without shallow option to update URL and reset state

B. Use router.push with { shallow: true } when changing tabs and listen to router.query to update UI

C. Reload the page on every tab click to fetch fresh data

D. Manually manipulate window.location to change URL without Next.js router

Solution

1. Step 1: Identify shallow routing usage for tab navigation

   Using router.push with { shallow: true } updates URL query without full reload, preserving component state.

2. Step 2: Confirm UI updates from router.query changes

   Listening to router.query allows UI to react to tab changes smoothly without losing state.

3. Final Answer:

   Use router.push with { shallow: true } and listen to router.query -> Option B

4. Quick Check:

   Shallow routing + query listening = smooth tab navigation [OK]

Hint: Use router.push with shallow and watch router.query [OK]

Common Mistakes:

• Reloading page loses component state
• Using router.replace without shallow resets state
• Manipulating window.location breaks SPA behavior