When it comes to frequently asked Vue.js interview questions, here are some frequently asked questions and their answers:
1. What is Vue.js? What are the characteristics?
Vue.js is a progressive JavaScript framework for building user interfaces. It has the following characteristics:
- Lightweight: The Vue.js core library only focuses on the view layer and is small in size.
- Easy to learn and use: With a simple and clear API, it is easy to get started and integrate into existing projects.
- Data-driven: Use declarative template syntax and automatically track data and DOM changes through two-way data binding.
- Componentization: Use component development thinking to split the interface into independent and reusable components.
- Rich ecology: It has a huge community and a powerful plug-in system, supporting seamless integration with other libraries or tools.
2. What is the MVVM pattern? What is the relationship between Vue.js architecture and MVVM?
MVVM refers to Model-View-ViewModel, which is a software architecture pattern. In MVVM, View is the user interface and ViewModel is the view model, responsible for communication and data binding between View and Model (data layer).
The architecture of Vue.js is tied to MVVM. The view part of Vue.js is View, and the data and state in the component are ViewModel. The responsive data binding system of Vue.js allows the data in the ViewModel to be updated synchronously with the View, helping developers manage and maintain the user interface more easily.
3. What is virtual DOM? Why use virtual DOM?
Virtual DOM is a core technology of Vue.js. It is a lightweight in-memory copy that stays in sync with the real DOM. When the data changes, Vue.js will compare the difference between the virtual DOM and the old virtual DOM to minimize the number of direct operations on the real DOM and improve rendering efficiency.
The benefits of using virtual DOM are:
- Improved performance: Operating the real DOM is expensive. By optimizing the virtual DOM, the user interface can be updated more efficiently.
- Cross-platform: Virtual DOM is platform-independent, allowing Vue.js to run in multiple environments such as browsers, servers, and mobile terminals.
- Simplify development: Through the abstraction of virtual DOM, developers can focus on business logic without paying too much attention to underlying DOM operations.
4. What are the life cycle hooks in Vue.js? When are they called?
Lifecycle hooks for Vue.js components include beforeCreate, created, beforeMount, mounted, beforeUpdate, updated, beforeDestroy and destroyed.
- beforeCreate: Perform some initialization tasks before the instance is created. Data and templates cannot be accessed at this time.
- created: After the instance is created, the data and templates can be accessed, but have not yet been mounted on the DOM.
- beforeMount: Called before the component is mounted to the DOM, final preparations can be made.
- mounted: Called after the component is mounted to the DOM. At this time, you can perform DOM operations and interact with the server.
- beforeUpdate: When responsive data is updated, it is called before re-rendering, and pre-update operations can be performed at this time.
- updated: Called after the component is re-rendered and updated. At this time, the DOM can be operated.
- beforeDestroy: Called before the component is destroyed, it can clear timers, unbind events and other operations.
- destroyed: Called after the component is destroyed to perform some cleanup work, such as unbinding global events, etc.