分享当下较新的30道Vue面试题！ (qq.com)

The difference between vue and angular?

Vue and Angular are both popular JavaScript frameworks used for building web applications. Here are some key differences between them:

1. Learning Curve: Vue.js is generally considered easier to learn than Angular. Vue.js has a simpler syntax and a smaller API surface area than Angular, making it easier for developers to pick up quickly.

2. Size: Vue.js is smaller in size compared to Angular, which can impact application performance. Angular is a more comprehensive framework with more features out of the box, which can make it a better choice for larger and more complex applications.

3. Templating: Vue.js uses a template-based syntax, while Angular uses a component-based syntax. This means that Vue.js can be easier to read and understand, but Angular provides more structure and organization for larger applications.

4. State Management: Vue.js has a built-in state management library called Vuex, while Angular uses the RxJS library for state management. Both solutions are effective, but Vuex is generally considered simpler and easier to use.

5. Performance: Vue.js is faster than Angular in terms of rendering speed and startup time. However, Angular has a more robust change detection system, which can improve application performance for large and complex applications.

Overall, the choice between Vue.js and Angular depends on the specific needs of your project. If you are looking for a lightweight, easy-to-learn framework for smaller applications, Vue.js may be the better choice. If you are building a larger, more complex application that requires a more comprehensive framework with more features out of the box, Angular may be a better choice.

What kind of technology Vue borrowed from angular and react?

Vue.js, like many modern front-end frameworks, has been influenced by both Angular and React. Here are some of the technologies that Vue has borrowed from these frameworks:

1. Virtual DOM: React introduced the concept of a Virtual DOM, which is a lightweight representation of the actual DOM tree. This allows React to update the UI more efficiently by only re-rendering the parts of the UI that have changed. Vue.js also uses a Virtual DOM to achieve high performance and efficient updates.

2. Components: Both Angular and React use a component-based architecture, where the UI is broken down into smaller reusable components. Vue.js also uses this approach, making it easy to create reusable components and build complex UIs.

3. Directives: Vue.js borrows the concept of directives from Angular. Directives are special HTML attributes that allow you to add behavior to an HTML element. Vue.js provides a number of built-in directives, and also allows you to create custom directives.

4. Dependency Injection: Angular uses a Dependency Injection (DI) system to manage dependencies between components. Vue.js doesn't have a built-in DI system, but it does allow you to pass props and events between components to achieve similar functionality.

5. Reactivity: Vue.js has borrowed the concept of reactivity from both Angular and React. Reactivity refers to the ability of a framework to automatically update the UI when data changes. Vue.js achieves this through its reactivity system, which tracks changes to data and automatically updates the UI as needed.

Overall, Vue.js has borrowed technologies from both Angular and React, but has also added its own unique features and approach to building web applications.

Does Vue borrow template and data-binding from Angular? or from other frameworks?

Vue.js borrows the concept of templates and data-binding from Angular, as well as other front-end frameworks.

Like Angular, Vue.js uses templates to define the structure and layout of the UI. Templates in Vue.js are similar to those in Angular, allowing you to use expressions and directives to manipulate the UI. Vue.js also supports two-way data-binding, which allows changes to the UI to update the underlying data model, and changes to the data model to update the UI. This approach is similar to the data-binding system used in Angular.

However, Vue.js also introduces its own unique approach to templates and data-binding. For example, Vue.js templates are written in plain HTML, with additional Vue-specific syntax for directives and expressions. This makes Vue.js templates easier to read and understand for developers who are familiar with HTML. Additionally, Vue.js uses a reactivity system to automatically update the UI when the underlying data changes, which is slightly different from the data-binding approach used in Angular.

Overall, Vue.js has borrowed concepts from Angular and other front-end frameworks, but has also introduced its own unique approach to building web applications.

Show me your understanding about Vue.js?

Vue.js is an open-source JavaScript framework used for building dynamic and reactive user interfaces. It was created by Evan You in 2014, and has gained widespread popularity among developers due to its simplicity, flexibility, and performance.

At its core, Vue.js is built around the concept of components. A Vue.js component is a reusable piece of UI that can be composed together to build more complex UIs. Components in Vue.js are defined using a combination of HTML-like templates, JavaScript code, and CSS styles. Vue.js also provides a powerful reactivity system, which automatically updates the UI when data changes.

One of the unique features of Vue.js is its approach to directives. Directives in Vue.js are special attributes that can be attached to HTML elements, and are used to provide additional behavior and functionality. Vue.js provides a number of built-in directives, such as v-if, v-for, and v-bind, and also allows developers to create custom directives.

Vue.js also provides a number of other features and tools, including a command-line interface for scaffolding and building projects, a state management library called Vuex, and a routing library called Vue Router.

In summary, Vue.js is a powerful and flexible framework for building dynamic and reactive user interfaces. Its focus on components, directives, and reactivity make it easy to create complex UIs, while its simplicity and performance make it a popular choice among developers.

But you do not mention MVVM?

You are correct that I did not explicitly mention the MVVM pattern in my previous answer. However, it's worth noting that Vue.js is often described as a framework that follows the MVVM (Model-View-ViewModel) architecture.

In the MVVM pattern, the View is responsible for displaying data to the user, the Model represents the data and business logic, and the ViewModel acts as a mediator between the View and the Model, providing an abstraction layer and handling user input and interaction.

In Vue.js, components can be thought of as the View, the data and business logic can be thought of as the Model, and the ViewModel can be thought of as the Vue instance that controls the component. The Vue instance provides the data and methods that the component needs, and handles user input and interaction through event listeners and directives.

So while I did not explicitly mention MVVM in my previous answer, the architecture of Vue.js is often described as following this pattern.

How does Vue implement reactive data?

Vue.js uses a reactivity system to implement reactive data. When you create a new Vue instance, Vue.js creates a reactive proxy object that represents the data for that instance.

When you modify the data in the reactive object, Vue.js detects the change and automatically updates the UI to reflect the new data. This allows you to create dynamic and reactive user interfaces without needing to manually update the UI every time the data changes.

Under the hood, Vue.js uses JavaScript's Object.defineProperty() method to define getters and setters for each property in the reactive object. When you read or modify a property, the getter or setter is called, which allows Vue.js to track when the property is read or modified.

When you modify a property, Vue.js queues up a re-render of the affected components. When the next tick of the event loop occurs, Vue.js checks the queue and updates the affected components, only updating the parts of the UI that have changed. This allows Vue.js to achieve high performance and efficient updates.

Overall, Vue.js's reactivity system provides a powerful and flexible way to create reactive data and dynamic user interfaces, without needing to manually update the UI every time the data changes.

Could you introduce the steps from initData, Observer, walk(value), defineReactive, defineProperty?

Sure, here is a detailed overview of the steps involved in creating reactive data in Vue.js:

1. Initialization: When you create a new Vue instance, Vue.js initializes the data object by calling the initData() function. This function creates a plain JavaScript object that contains the initial data for the instance.

2. Observer: Vue.js then creates an Observer instance, which recursively walks through the data object and converts each property into a getter/setter using the defineReactive() function. The Observer is responsible for tracking dependencies and notifying the appropriate Watcher instances when a property is modified.

3. Walk: The walk() function is called by the Observer to recursively walk through the data object and convert each property into a getter/setter. The walk() function uses the defineReactive() function to define the getter/setter for each property.

4. defineReactive: The defineReactive() function is responsible for defining a getter/setter for a given property. The getter returns the current value of the property, and the setter updates the value of the property and notifies any Watcher instances that depend on the property.

5. defineProperty: The defineReactive() function uses the Object.defineProperty() method to define the getter/setter for a given property. This method defines the property as non-enumerable, meaning that it won't appear in for...in loops or the Object.keys() method.

Overall, this process allows Vue.js to create reactive data that automatically updates the UI when the data changes, without needing to manually update the UI every time the data changes. The reactive data system in Vue.js is efficient and flexible, allowing for dynamic and reactive user interfaces.

How does Vue detect modifications when the array changes?

In Vue.js, detecting modifications to arrays is a bit more complex than detecting modifications to objects because arrays in JavaScript are not reactive by default.

To detect modifications to arrays, Vue.js uses a technique called "array observation." When you modify an array (e.g., by calling push(), pop(), splice(), etc.), Vue.js detects the modification by intercepting the array methods and triggering a re-render of the affected components.

Here is an overview of the steps involved in detecting modifications to arrays in Vue.js:

1. Initialization: When you create a new Vue instance, Vue.js initializes the data object and converts it into a reactive proxy object using the reactive() function.

2. Array observation: Vue.js creates a separate Observer instance for each reactive array in the data object. This Observer instance overrides the original array methods (e.g., push(), pop(), splice(), etc.) with "interceptor" methods that call the original method and then trigger a re-render of the affected components.

3. Mutation: When you modify a reactive array (e.g., by calling push(), pop(), splice(), etc.), Vue.js intercepts the method call and calls the original method. After the method call is complete, Vue.js triggers a re-render of the affected components using a queue that tracks which components need to be re-rendered.

4. Diffing and patching: After the re-render queue is processed, Vue.js uses a diffing algorithm to determine which parts of the UI need to be updated. The updated parts of the UI are then patched, or updated, to reflect the new data.

Overall, this array observation technique allows Vue.js to detect modifications to arrays and update the UI accordingly, providing a powerful and flexible way to create dynamic and reactive user interfaces.

Lifecycle of Vue.js

The lifecycle of a Vue.js instance refers to the sequence of stages that a Vue.js component goes through from its creation to its destruction. These stages are:

1. Creation: In this stage, Vue.js initializes the component's data, creates computed properties and methods, and sets up event listeners and watchers. This stage starts when a new Vue.js instance is created using the Vue constructor.

2. Mounting: In this stage, Vue.js compiles the component's template into a virtual DOM and creates a real DOM node that corresponds to the component. The component is then inserted into the document at the specified location. This stage starts when Vue.js calls the component's $mount() method.

3. Updating: In this stage, Vue.js detects changes to the component's data and updates the virtual DOM tree accordingly. If the changes affect the component's UI, Vue.js will patch the real DOM to reflect the updated virtual DOM. This stage starts when the component's data changes and ends when the real DOM is updated.

4. Destruction: In this stage, Vue.js removes the component from the document, unbinds any event listeners, and cleans up any memory used by the component. This stage starts when the component is destroyed using the $destroy() method.

During each stage of the lifecycle, Vue.js provides several lifecycle hooks that allow you to execute custom code at specific points in the component's lifecycle. These hooks include:

• beforeCreate: executed before the component is created
• created: executed when the component is created, but before it is mounted
• beforeMount: executed before the component is mounted
• mounted: executed after the component is mounted
• beforeUpdate: executed before the component is updated
• updated: executed after the component is updated
• beforeDestroy: executed before the component is destroyed
• destroyed: executed after the component is destroyed

By using these hooks, you can customize the behavior of your Vue.js components at various points in their lifecycle. This allows you to perform custom initialization, cleanup, or other operations as needed.