Computed properties for derived state in Vue - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a computed property in Vue?

A computed property is a special function that automatically calculates and updates a value based on reactive data. It caches the result and only recalculates when its dependencies change.

beginner

Why use computed properties instead of methods for derived state?

Computed properties cache their results and only update when dependencies change, making them more efficient than methods, which run every time they are called.

intermediate

How do you define a computed property using the Composition API in Vue 3?

You import the 'computed' function from 'vue' and pass a function that returns the derived value. Example: const fullName = computed(() => firstName.value + ' ' + lastName.value);

beginner

What happens if a computed property depends on reactive data that changes?

The computed property automatically recalculates its value and updates any parts of the UI that use it, keeping the interface in sync with the data.

intermediate

Can computed properties have setters in Vue? What is their use?

Yes, computed properties can have setters to allow two-way binding. The setter lets you update the underlying reactive data when the computed property is assigned a new value.

What does a computed property in Vue do?

A Calculates a value and caches it until dependencies change

B Runs every time the component renders without caching

C Directly modifies the DOM elements

D Stores static data that never changes

Computed properties calculate values based on reactive data and cache the result until dependencies change.

Which Vue API is used to create a computed property in Vue 3 Composition API?

A reactive()

B ref()

C computed()

D watch()

The computed() function creates computed properties that derive values from reactive data.

When does a computed property recalculate its value?

A When one of its reactive dependencies changes

B Every time the component renders

C Only when the component mounts

D When the user clicks a button

Computed properties recalculate only when their reactive dependencies change, improving efficiency.

What is the benefit of using a computed property over a method for derived state?

A Computed properties can modify data directly

B Methods automatically cache results

C Methods are faster than computed properties

D Computed properties cache results and avoid unnecessary recalculations

Computed properties cache their results and only update when dependencies change, unlike methods.

Can computed properties in Vue have setters?

A No, they are read-only

B Yes, to allow two-way data binding

C Only in Vue 2

D Only if you use methods

Computed properties can have setters to update reactive data, enabling two-way binding.

Explain how computed properties help keep the UI in sync with data in Vue.

Think about how Vue tracks changes and updates the screen.

Describe how to create a computed property using Vue 3 Composition API and why it is preferred over methods for derived state.

Focus on the syntax and benefits of computed properties.