RouterLink for navigation in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is RouterLink used for in Angular?

RouterLink is a directive that lets you navigate between different views or pages in an Angular app by linking to routes defined in the router configuration.

beginner

How do you use RouterLink in a template to navigate to a route named 'home'?

You add [routerLink]="['/home']" to an anchor tag like this: <a [routerLink]="['/home']">Home</a>. Clicking it navigates to the 'home' route.

intermediate

What is the difference between using routerLink and a normal href for navigation?

routerLink changes the view without reloading the whole page, keeping the app fast and smooth. href reloads the entire page, which is slower and loses app state.

intermediate

How can you pass route parameters using RouterLink?

You pass parameters as part of the array, for example: [routerLink]="['/product', productId]". This navigates to a route like '/product/123' if productId is 123.

intermediate

What attribute can you use with RouterLink to add CSS classes when the link is active?

You use routerLinkActive to add CSS classes when the linked route is active. Example: <a [routerLink]="['/home']" routerLinkActive="active">Home</a>.

What does [routerLink]="['/about']" do in an Angular template?

A Reloads the entire page and goes to '/about'

B Navigates to the 'about' route without reloading the page

C Creates a button that submits a form

D Adds a CSS class named 'about'

routerLink changes the view by navigating to the route without a full page reload.

How do you pass a parameter '42' to a route named 'item' using RouterLink?

A [routerLink]="['/item?id=42']"

B [routerLink]="['/item']" param="42"

C routerLink="/item/42"

D [routerLink]="['/item', 42]"

Parameters are passed as array elements after the route path.

Which directive adds a CSS class when the linked route is active?

A routerLinkActive

B routerLinkClass

C activeLink

D routerActive

routerLinkActive adds CSS classes when the route matches the link.

What happens if you use a normal href instead of routerLink in Angular navigation?

A It throws an error

B Angular intercepts and navigates without reload

C The page reloads completely

D Nothing happens

href causes a full page reload, unlike routerLink.

Which of these is the correct way to write a RouterLink for the root path?

A [routerLink]="['/']"

B [routerLink]="['home']"

C routerLink="root"

D [routerLink]="['root']"

The root path is represented by '/' in the routerLink array.

Explain how RouterLink helps in navigating between pages in an Angular app without reloading the page.

Think about how single-page apps work.

Describe how to pass parameters to routes using RouterLink and how to highlight active links.

Focus on syntax and styling active links.

Practice

1. What is the main purpose of RouterLink in Angular?

easy

A. To fetch data from a server

B. To style buttons with CSS classes

C. To create clickable links that navigate within the app without reloading the page

D. To define routes in the app module

Solution

1. Step 1: Understand RouterLink's role

   RouterLink is used to create links that change the URL and navigate inside the Angular app smoothly.

2. Step 2: Differentiate from other features

   It does not style buttons, fetch data, or define routes; those are separate tasks.

3. Final Answer:

   To create clickable links that navigate within the app without reloading the page -> Option C

4. Quick Check:

   RouterLink = navigation links [OK]

Hint: RouterLink changes URL inside app without page reload [OK]

Common Mistakes:

• Confusing RouterLink with CSS styling
• Thinking RouterLink fetches data
• Mixing RouterLink with route definitions

2. Which of the following is the correct syntax to create a static link to '/home' using RouterLink in a template?

easy

A. Home

B. Home

C. Home

D. Home

Solution

1. Step 1: Identify static RouterLink syntax

   For static paths, use routerLink="/path" without square brackets.

2. Step 2: Check each option

   <a routerLink="['/home']">Home</a> (A) uses array literal as static string, leading to malformed path. <a [routerLink]="/home">Home</a> (B) has invalid binding expression (missing string quotes). <a routerLink=['/home']>Home</a> (C) has wrong brackets syntax without quotes. <a routerLink="/home">Home</a> (D) uses correct static syntax.

3. Final Answer:

   <a routerLink="/home">Home</a> -> Option D

4. Quick Check:

   Static link = no brackets [OK]

Hint: Static links use routerLink without square brackets [OK]

Common Mistakes:

• Using square brackets for static strings unnecessarily
• Missing leading slash in path
• Incorrect bracket placement

3. Given the component template:

<a [routerLink]="['/profile', userId]">Profile</a>

and userId = 42, what URL will the link navigate to when clicked?

medium

A. /profile?userId=42

B. /profile/42

C. /profile/userId

D. /profile

Solution

1. Step 1: Understand array syntax in RouterLink

   Using [routerLink]="['/profile', userId]" creates a URL by joining segments, so it appends userId as a path segment.

2. Step 2: Substitute userId value

   With userId = 42, the URL becomes /profile/42.

3. Final Answer:

   /profile/42 -> Option B

4. Quick Check:

   Array routerLink joins segments with slashes [OK]

Hint: Array syntax adds path segments separated by slashes [OK]

Common Mistakes:

• Thinking it adds query parameters instead of path segments
• Using string interpolation inside array incorrectly
• Ignoring dynamic value substitution

4. Identify the error in this RouterLink usage:

<a [routerLink]="'/dashboard'">Dashboard</a>

medium

A. The binding brackets should be removed for static paths

B. RouterLink cannot be used on <a> tags

C. The path string should not be in quotes inside the binding brackets

D. Missing parentheses around the path

Solution

1. Step 1: Analyze binding syntax

   Using square brackets means Angular expects an expression. Here, the expression is a string literal with quotes, which is valid but unnecessary for static paths.

2. Step 2: Correct usage for static paths

   For static paths, remove square brackets and quotes: routerLink="/dashboard".

3. Final Answer:

   The binding brackets should be removed for static paths -> Option A

4. Quick Check:

   Static path = no brackets [OK]

Hint: Remove brackets for static string paths [OK]

Common Mistakes:

• Using quotes inside binding brackets unnecessarily
• Thinking RouterLink can't be on anchor tags
• Adding parentheses around path

5. You want to create a navigation link that goes to a user detail page with a dynamic user ID, but only if the ID is valid (non-null). Which is the best way to use RouterLink in the template to handle this condition?

hard

A. User Details

B. User Details

C. User Details

D. User Details

Solution

1. Step 1: Understand conditional RouterLink binding

   <a [routerLink]="userId ? ['/user', userId] : ['/user']">User Details</a> uses a ternary operator inside the binding to choose the path based on userId validity, which is clean and safe.

2. Step 2: Evaluate other options

   <a *ngIf="userId" [routerLink]="['/user', userId]">User Details</a> hides the link if userId is falsy, which may be okay but removes the link entirely. <a [routerLink]="['/user', userId || 'default']">User Details</a> uses a fallback string which might not be desired. <a [routerLink]="/user/{{userId}}">User Details</a> uses interpolation inside the binding expression, which is invalid template syntax.

3. Final Answer:

   <a [routerLink]="userId ? ['/user', userId] : ['/user']">User Details</a> -> Option A

4. Quick Check:

   Use ternary inside binding for conditional paths [OK]

Hint: Use ternary operator inside [routerLink] for conditions [OK]

Common Mistakes:

• Using interpolation inside routerLink attribute
• Hiding link instead of changing path
• Using fallback strings that may confuse routing