Vue.js Basics

What is Vue.js?

Vue.js is a progressive JavaScript framework used for building user interfaces and single-page applications. It is designed to be incrementally adoptable, meaning that you can use it to enhance existing projects or build complex applications from scratch.

What are the core features of Vue.js?

The core features of Vue.js include:

• Reactivity: Vue.js utilizes a reactive data-binding system that automatically updates the UI when the underlying data changes.
• Components: Vue.js allows developers to create reusable components that encapsulate HTML, CSS, and JavaScript, promoting modularity and reusability.
• Directives: Vue.js provides special attributes called directives (e.g., v-bind, v-model, v-if) that enhance HTML with dynamic behavior.
• Vue Router: A routing library for creating single-page applications by allowing navigation between components.
• Vuex: A state management library for managing complex state in larger applications.

How do you create a new Vue instance?

You can create a new Vue instance by using the new Vue() constructor, passing an options object that defines the data, methods, and lifecycle hooks.

const app = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  },
  methods: {
    greet() {
      console.log(this.message);
    }
  }
});

What is the purpose of the el property in a Vue instance?

The el property specifies the DOM element that the Vue instance will manage. It serves as the mounting point for the Vue application, allowing Vue to control the specified element and its children.

<div id="app">
  {{ message }}
</div>

const app = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  }
});

What are Vue directives?

Vue directives are special attributes that provide functionality to HTML elements. They are prefixed with v- and are used to bind data or control the rendering of elements in the template. Some common directives include:

• v-bind: Dynamically binds one or more attributes to an expression.
• v-model: Creates two-way data binding on form input elements.
• v-if: Conditionally renders an element based on a boolean expression.
• v-for: Renders a list of elements based on an array.

How does the reactivity system in Vue.js work?

Vue.js utilizes a reactive data-binding system that makes use of getters and setters to track changes to data properties. When a data property changes, Vue automatically re-renders the component and updates the DOM to reflect the new state.

const app = new Vue({
  el: '#app',
  data: {
    count: 0
  }
});

// Change the count
app.count++; // Automatically updates the DOM where count is displayed

What is the Vue instance lifecycle?

The Vue instance lifecycle consists of various stages, each with its own lifecycle hooks. The main lifecycle stages are:

• Creation: The instance is created, and the data is initialized.
• Mounting: The instance is mounted to the DOM.
• Updating: The instance updates when data changes.
• Destruction: The instance is destroyed, and cleanup is performed.

Common lifecycle hooks include:

• created: Called after the instance is created.
• mounted: Called after the instance is mounted to the DOM.
• updated: Called after the data changes and the DOM is re-rendered.
• beforeDestroy: Called right before the instance is destroyed.

How do you pass data to child components in Vue.js?

Data can be passed to child components through props. Props are custom attributes that can be defined on a child component, allowing it to receive data from its parent.

Vue.component('child-component', {
  props: ['message'],
  template: '<div>{{ message }}</div>'
});

new Vue({
  el: '#app',
  data: {
    parentMessage: 'Hello from Parent!'
  },
  template: '<child-component :message="parentMessage"></child-component>'
});

What is Vue Router and why is it used?

Vue Router is the official router for Vue.js that allows developers to create single-page applications with navigation between different views or components. It provides features such as nested routes, dynamic routing, and route parameters, making it easier to manage application state and navigation.

// Example of Vue Router setup
const router = new VueRouter({
  routes: [
    { path: '/home', component: HomeComponent },
    { path: '/about', component: AboutComponent }
  ]
});

const app = new Vue({
  router
}).$mount('#app');

What is Vuex and when should you use it?

Vuex is a state management library for Vue.js applications. It provides a centralized store for managing application state in a predictable way. Vuex is particularly useful for larger applications where multiple components need to share and manage state, providing a clear structure and making state mutations more manageable.

// Example Vuex store
const store = new Vuex.Store({
  state: {
    count: 0
  },
  mutations: {
    increment(state) {
      state.count++;
    }
  }
});

const app = new Vue({
  store,
  computed: {
    count() {
      return this.$store.state.count;
    }
  }
});