day07 interview questions

1.Have you ever used vue? Tell me about your understanding of vue

As an AI assistant, I don't have my own practical experience, but I can provide you with information about Vue.js based on my knowledge base.

Vue.js is a popular JavaScript front-end framework for building user interfaces. It is based on the MVVM (Model-View-ViewModel) pattern and allows developers to more easily build interactive and reusable web interfaces by using concise template syntax and responsive data binding.

The following is some of my understanding of Vue.js:

1. Component-based development: Vue.js encourages the use of component-based methods to build user interfaces. Developers can split pages into independent, reusable components, each responsible for its own logic and styling, and then build complete applications by combining these components. This component-based development approach makes the code more modular and improves development efficiency and maintainability.

2. Responsive data binding: Vue.js adopts a two-way data binding mechanism. By binding the data model and the view, the view will automatically update when the data changes. This responsive data binding feature reduces the need for manual DOM manipulation and simplifies the development process.

3. Virtual DOM: Vue.js minimizes real DOM operations by using virtual DOM technology. When the data changes, Vue.js will compare the difference between the virtual DOM and the real DOM and only update the changed parts, thereby improving performance.

4. Ecosystem: Vue.js has a huge ecosystem, including officially maintained core libraries, plug-ins, tools, etc. Among them, the officially maintained Vue Router is used to handle front-end routing, Vuex is used for state management, and there are many third-party plug-ins and components for developers to use.

Generally speaking, Vue.js has simple and elegant syntax, flexible component-based development model and efficient responsive data binding mechanism, making front-end development more efficient and enjoyable. It's relatively easy to get started and suitable for building web applications of all sizes.

2. What is your understanding of SPA single page and what are its advantages and disadvantages? How to implement SPA application

Single Page Application (SPA) is an architectural pattern for web applications that loads an HTML page upon initialization and dynamically updates the page's content through JavaScript without reloading the entire page.

Here is a brief overview of the advantages and disadvantages of SPA:

advantage:

1. Better user experience: Since SPA only needs to be loaded once, subsequent page switching is partially updated through AJAX or JavaScript, which can achieve fast and smooth page switching and provide a smoother user experience.
2. Reduce server load: Because SPA only needs to obtain data from the server without repeatedly transmitting HTML, it reduces requests to the server and reduces server load.
3. High reusability: SPA adopts a component-based development method, and components can be reused between different pages, reducing code redundancy and improving development efficiency and maintainability.
4. Fast response: Since SPA communicates asynchronously with the backend, it can obtain data and update the page through AJAX requests, thereby achieving fast response and reducing waiting time.

shortcoming:

1. Slow first load: SPA needs to load all required HTML, CSS and JavaScript files at once, so the first load time is relatively long.
2. SEO (search engine optimization) challenges: Since SPA mainly dynamically generates content through JavaScript, search engine crawlers may not be able to obtain the complete content when crawling the page, which has a certain impact on SEO. But modern search engines can already handle some SPA applications.
3. High memory usage: Since SPA loads and renders a large amount of content on one page, it may result in high memory usage.
4. Browser compatibility: Some older versions of browsers have incomplete support for HTML5, CSS3 and JavaScript and may not be able to run SPA applications properly.

The main way to implement SPA applications is to manage dynamic updates of routing and views through JavaScript frameworks (such as Vue.js, React.js, Angular, etc.). These frameworks provide a front-end routing mechanism that can load corresponding components or modules according to URL changes and insert them into specific areas of the page to achieve single page switching and updating. At the same time, AJAX technology is used for data requests and responses to achieve asynchronous communication with the backend.

3. How to solve the slow loading speed of the SPA first screen?

In order to solve the problem of slow loading speed of the SPA first screen, you can take the following measures:

1. Code Splitting: Splitting the entire application into multiple modules or code blocks and loading each module only when needed instead of loading the entire application at once. This can be achieved by using the dynamic import feature of a packaging tool such as webpack.

2. Route Lazy Loading: For routes in large applications, the components corresponding to each route can be loaded lazily, and the corresponding components are only loaded when the route is accessed. This reduces the amount of content to be loaded on first load.

3. Static resource caching: Make reasonable use of the browser caching mechanism to cache static resources that do not change frequently (such as CSS and JavaScript files) for a long time to reduce repeated downloading and loading.

4. Image optimization: For large images that may exist on the page, you can compress, delay loading (lazy loading), or use progressive image loading based on the Intersection Observer API to improve the loading speed of the first screen.

5. Data prefetching and preloading: Data related to the current page can be prefetched or preloaded before the user accesses it to avoid requesting data only when the user interacts, thus speeding up page rendering.

6. Use CDN acceleration: Deploy static resources to a content distribution network (CDN), which can provide users with faster resource acquisition speed with the help of globally distributed nodes.

7. Optimize network requests: merge multiple network requests to reduce the number of requests; use the HTTP/2 protocol to improve transmission efficiency; compress request and response data and other methods to speed up network requests.

8. Front-end performance optimization: Optimize the code to eliminate unnecessary repeated calculations, avoid low-performance operations, and improve JavaScript execution efficiency. Tools can be used for performance analysis, identifying bottlenecks and optimizing them.

By combining the above measures, the first screen loading speed of SPA applications can be significantly improved and provide a better user experience.

4.Principle of VUE routing

The principle of Vue routing is based on the Vue Router plug-in, which uses front-end routing to implement page switching and navigation in single page applications (SPA).

1. Routing configuration: In a Vue application, you first need to configure routing. By creating a router instance and defining routing rules, that is, specifying the mapping relationship between URL paths and corresponding components. Nested routing, dynamic routing, named routing, etc. can be configured.

2. Route registration: Register the router instance into the Vue root instance so that it can be used by the entire application.

3. Route exit: In the Vue template, use <router-view>labels as placeholders to display the component content matched by the current route. Whenever the URL changes, the router selects the appropriate component based on routing rules and renders it into it <router-view>.

4. Routing navigation: Routing navigation will be triggered when the user enters a URL in the browser address bar, clicks on a page link, or triggers a route jump programmatically. The navigation process is managed by the router, which will find the corresponding component and switch pages based on the routing rules matched by the current URL.

5. Responsive update: When the URL changes, if the matched routing rules change, the router will trigger a responsive update, that is, re-render the matched component. In this way, dynamic switching of pages can be achieved and the data status between components can be maintained.

6. Routing parameter transfer: Data can be transferred to the target component through routing parameters, query parameters or routing meta-information to achieve communication and data sharing between components.

In general, the principle of Vue routing is to realize navigation in single-page applications by monitoring changes in the URL, selecting appropriate components for rendering according to the configured routing rules, and implementing responsive updates of data when the page switches. and page jump function.

5.What is the difference between components and plug-ins in Vue?

In Vue, components and plug-ins are both ways to extend the functionality of Vue applications, but they have some differences.

1. Components: Components are the basic building blocks in Vue applications, used to encapsulate reusable code and UI elements. By splitting the page into multiple components, the maintainability and reusability of the code can be improved. Components are composed of templates, JavaScript code and styles, and can contain data, methods, life cycle hooks, etc. In Vue, components have their own scope and private state, can be reused by other components, and can communicate with other components.

2. Plugins: Plug-ins are pluggable modules in Vue applications, used to add global functionality to Vue applications or extend Vue's core functionality. Plug-ins can contain a series of directives, filters, mix-in objects, instance methods, static methods and other features, as well as modifications to global configuration, prototype extensions and event handling. By installing a plug-in, you can use the functions provided by the plug-in throughout the entire Vue application without the need to introduce and configure each component separately.

To sum up, components are suitable for encapsulating UI and behavior to achieve local functions and reuse; plug-ins are used for global function expansion and sharing, affecting the entire Vue application. Components focus more on local-scale encapsulation and interaction, while plug-ins focus more on global-level functional expansion and configuration. Complex pages and applications can be built using components, while plug-ins provide Vue with more extensibility and flexibility.

6.What are the communication methods between Vue components?

In Vue, components can communicate with each other in a variety of ways. Common communication methods include:

1. Parent-child component communication: The parent component passes data to the child component through props, and the child component sends messages to the parent component through $emit trigger events.

2. Child-parent component communication: The child component triggers a custom event through $emit, and the parent component listens to the child component's event through v-on, and receives the data passed by the child component in the event handling function.

3. Sibling component communication: Communication between sibling components can be achieved by sharing the state of the parent component or using an empty Vue instance as an event bus.

4. Cross-level component communication: You can provide data in the parent component through the provide/inject API, and then use inject to obtain the corresponding data in the descendant components.

5. Use Vuex: Vuex is the state management library officially recommended by Vue, which can centrally manage application status and realize communication between components.

6. Use the event bus: Create an empty Vue instance as the event bus, and pass emit and emit in the components that need to communicate.$Theemitand\; on\; methodsdispatch$ and listen for events.

7. Use the publish-subscribe model: You can use third-party libraries such as EventBus or implement a simple publish-subscribe mechanism yourself to achieve decoupled communication between components.

Depending on actual needs and scenarios, choosing the appropriate communication method can facilitate and flexibly realize data exchange and sharing between components.