Enter and leave animations in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the animation trigger function.

Angular

import { [1] } from '@angular/animations';

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

Astyle

Banimate

Ctrigger

Dstate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'animate' instead of 'trigger' in the import.

Confusing 'style' with the trigger function.

The trigger function defines an animation trigger in Angular.

2fill in blank

medium

Complete the code to define an enter animation using opacity.

Angular

transition(':enter', [style({ opacity: 0 }), [1]('500ms ease-in', style({ opacity: 1 }))])

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

Akeyframes

Btrigger

Cstate

Danimate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'trigger' inside the transition array.

Using 'state' instead of 'animate' for timing.

The animate function defines the timing and style changes for the animation.

3fill in blank

hard

Fix the error in the leave animation transition.

Angular

transition(':leave', [[1]('300ms ease-out', style({ opacity: 0 }))])

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

Aanimate

Btrigger

Cstyle

Dstate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'trigger' instead of 'animate' inside transition.

Using 'style' alone without 'animate'.

The animate function is required to specify the animation timing and style changes.

4fill in blank

hard

Fill both blanks to create a fade in and fade out animation.

Angular

animations: [trigger('fade', [transition(':enter', [[1](0), [2]('400ms ease-in', style({ opacity: 1 }))]), transition(':leave', [[2]('400ms ease-out', style({ opacity: 0 }))])])]

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

Astyle

Banimate

Ctrigger

Dstate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'animate' where 'style' is needed for initial styles.

Mixing up the order of 'style' and 'animate'.

style sets the initial or final styles, and animate defines the animation timing and transition.

5fill in blank

hard

Fill all three blanks to define a slide in and slide out animation.

Angular

animations: [trigger('slide', [transition(':enter', [[1]({ transform: 'translateX(-100%)' }), [2]('300ms ease-out', style({ transform: 'translateX(0)' }))]), transition(':leave', [[2]('300ms ease-in', style({ transform: 'translateX(-100%)' })), [3]('*')])])]

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

Astyle

Banimate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'animate' where 'style' is needed for initial position.

Omitting the last style reset causing animation glitches.

Use style to set start/end positions and animate to define timing. The last blank resets styles instantly.

Practice

1. What do :enter and :leave states represent in Angular animations?

easy

A. They define animations for when elements appear and disappear.

B. They control the timing of all animations globally.

C. They are used to pause and resume animations.

D. They specify styles for static elements only.

Solution

1. Step 1: Understand Angular animation states

   The :enter state triggers when an element is added to the DOM, and :leave triggers when it is removed.

2. Step 2: Identify their purpose

   These states allow defining animations specifically for elements appearing or disappearing, making transitions smooth.

3. Final Answer:

   They define animations for when elements appear and disappear. -> Option A

4. Quick Check:

   :enter and :leave = animations for appear/disappear [OK]

Hint: Remember :enter = appear, :leave = disappear animations [OK]

Common Mistakes:

• Thinking :enter and :leave control global animation timing
• Confusing :enter/:leave with pausing animations
• Assuming they apply only to static elements

2. Which of the following is the correct syntax to define an enter animation trigger in Angular?

easy

A. trigger('fadeIn', [transition('enter', [animate('500ms')])])

B. trigger('fadeIn', [state(':enter', style({opacity: 1}))])

C. trigger('fadeIn', [animate(':enter', style({opacity: 1}))])

D. trigger('fadeIn', [transition(':enter', [style({opacity: 0}), animate('500ms', style({opacity: 1}))])])

Solution

1. Step 1: Recall Angular animation syntax

   Enter animations use transition(':enter', [...]) inside a trigger with defined styles and animate calls.

2. Step 2: Check each option

   trigger('fadeIn', [transition(':enter', [style({opacity: 0}), animate('500ms', style({opacity: 1}))])]) correctly uses transition(':enter', [style(...), animate(...)]). The distractors misuse state, animate directly, or wrong transition name.

3. Final Answer:

   trigger('fadeIn', [transition(':enter', [style({opacity: 0}), animate('500ms', style({opacity: 1}))])]) -> Option D

4. Quick Check:

   Use transition(':enter', [...]) inside trigger [OK]

Hint: Use transition(':enter', [...]) inside trigger for enter animations [OK]

Common Mistakes:

• Using state() instead of transition() for :enter
• Writing 'enter' without colon in transition
• Calling animate() outside transition

3. Given this Angular animation trigger:

trigger('slideInOut', [
  transition(':enter', [style({transform: 'translateX(-100%)'}), animate('300ms ease-out', style({transform: 'translateX(0%)'}))]),
  transition(':leave', [animate('300ms ease-in', style({transform: 'translateX(100%)'}))])
])

What happens when an element with this trigger is removed from the DOM?

medium

A. It instantly disappears without animation.

B. It slides in from the left over 300ms.

C. It slides out to the right over 300ms.

D. It slides out to the left over 300ms.

Solution

1. Step 1: Analyze the :leave transition

   The :leave transition animates the element with animate('300ms ease-in', style({transform: 'translateX(100%)'})), moving it to the right (100%).

2. Step 2: Understand the effect on removal

   When the element is removed, it slides out to the right over 300 milliseconds before disappearing.

3. Final Answer:

   It slides out to the right over 300ms. -> Option C

4. Quick Check:

   :leave moves element right = slides out right [OK]

Hint: Check :leave style transform direction for exit animation [OK]

Common Mistakes:

• Confusing :enter and :leave animations
• Assuming instant disappearance without animation
• Mixing left and right directions

4. Identify the error in this Angular animation trigger code:

trigger('fade', [
  transition(':enter', [animate('500ms', style({opacity: 1}))]),
  transition(':leave', [style({opacity: 1}), animate('500ms', style({opacity: 0}))])
])

medium

A. Missing initial style for :enter transition.

B. Incorrect use of animate() inside transition.

C. Using style() after animate() in :leave transition.

D. No error; code is correct.

Solution

1. Step 1: Review :enter transition

   The :enter transition animates from current style to opacity 1 but lacks an initial style with opacity 0, so it jumps instead of fading in.

2. Step 2: Check :leave transition

   The :leave transition correctly starts at opacity 1 and animates to opacity 0.

3. Final Answer:

   Missing initial style for :enter transition. -> Option A

4. Quick Check:

   :enter needs starting style for smooth fade [OK]

Hint: Always set initial style before animate() in :enter [OK]

Common Mistakes:

• Omitting initial style in :enter causes jump
• Thinking animate() usage is wrong here
• Confusing order of style() and animate()

5. You want to create an Angular animation that fades an element in when it appears and slides it out to the left when it disappears. Which trigger definition correctly combines these enter and leave animations?

hard

A. trigger('fadeSlide', [transition(':enter', [animate('400ms', style({opacity: 1}))]), transition(':leave', [style({transform: 'translateX(-100%)'}), animate('400ms')])])

B. trigger('fadeSlide', [transition(':enter', [style({opacity: 0}), animate('400ms', style({opacity: 1}))]), transition(':leave', [animate('400ms', style({transform: 'translateX(-100%)'}))])])

C. trigger('fadeSlide', [transition(':enter', [style({opacity: 1}), animate('400ms', style({opacity: 0}))]), transition(':leave', [animate('400ms', style({transform: 'translateX(100%)'}))])])

D. trigger('fadeSlide', [transition(':enter', [style({opacity: 0}), animate('400ms', style({opacity: 1}))]), transition(':leave', [animate('400ms', style({transform: 'translateX(100%)'}))])])

Solution

1. Step 1: Check :enter animation for fade in

   transition(':enter', [style({opacity: 0}), animate('400ms', style({opacity: 1}))]) correctly fades in from opacity 0 to 1.

2. Step 2: Check :leave animation for slide out left

   transition(':leave', [animate('400ms', style({transform: 'translateX(-100%)'}))]) slides the element to the left.

3. Step 3: Verify other options

   Distractors fail by missing initial opacity 0 (no fade-in), reversing fade direction, using wrong slide direction (+100% right), or incomplete animate call.

4. Final Answer:

   trigger('fadeSlide', [transition(':enter', [style({opacity: 0}), animate('400ms', style({opacity: 1}))]), transition(':leave', [animate('400ms', style({transform: 'translateX(-100%)'}))])]) -> Option B

5. Quick Check:

   Fade in opacity 0->1, slide out left translateX(-100%) [OK]

Hint: Fade in needs opacity 0 start; slide left uses translateX(-100%) [OK]

Common Mistakes:

• Forgetting initial opacity 0 on enter
• Using translateX(100%) instead of -100% for left slide
• Reversing fade directions