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Vue JS Interview Questions

Vue JS is a progressive JavaScript framework that’s approachable, versatile, and performant. It’s ideal for building interactive UIs and SPAs.

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Vue.js is a progressive JavaScript framework for building user interfaces. Unlike other frameworks like Angular or React, Vue is designed to be incrementally adoptable, making it easier to integrate with existing projects. Its core library focuses on the view layer only, allowing developers to create single-page applications (SPAs) with ease.

Here’s a step-by-step comparison:

  1. Design Philosophy: Vue is more flexible and less opinionated, allowing for easier integration.
  2. Learning Curve: Vue has a gentle learning curve, ideal for beginners.
  3. Size: Vue is lightweight, making it faster to load and execute.

For example, integrating Vue into an existing HTML page is as simple as including a CDN link:

<script src="https://cdn.jsdelivr.net/npm/vue@2"></script>
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A Vue component is a reusable instance with its own data, methods, and lifecycle. It helps in breaking down the UI into smaller, manageable parts. To create a component, you can use the Vue.component method or the newer SFC (Single File Component) structure.

Follow these steps to create a simple component:

  1. Define the component: Use the Vue.component method.
  2. Template: Create a template that outlines the HTML structure.
  3. Script: Define the data and methods.

Here’s an example of a simple Vue component:

Vue.component('my-component', {
  template: '<div>Hello, {{ name }}!</div>',
  data: function() {
    return { name: 'Vue' };
  }
});
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Vue directives are special tokens in the markup that tell the library to do something to a DOM element. They are prefixed with a v- to indicate that they are Vue-specific. Directives provide reactive functionality and enhance the template syntax.

Here’s how they work:

  1. Binding: Directives bind data to the DOM.
  2. Modifiers: You can apply modifiers to alter the directive's behavior.
  3. Examples: Common directives include v-bind, v-model, and v-for.

Example of using v-bind:

<div v-bind:class="{ active: isActive }">Hello</div>
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Vue.js utilizes a reactive data model, meaning that the UI automatically updates when the underlying data changes. For complex applications, Vuex is a state management library specifically designed for Vue.

Here’s how Vuex works:

  1. Store: Create a central store to manage state.
  2. Actions: Define actions that can change the state.
  3. Getters: Use getters to access state in components.

Here’s an example of a simple Vuex store:

const store = new Vuex.Store({
  state: { count: 0 },
  mutations: { increment(state) { state.count++ } }
});
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The Vue lifecycle refers to the series of stages a Vue instance goes through from creation to destruction. Understanding the lifecycle hooks allows developers to execute code at specific points in a component's life, such as before it renders or after it updates.

Key stages include:

  1. Creation: beforeCreate, created
  2. Mounting: beforeMount, mounted
  3. Updating: beforeUpdate, updated
  4. Destruction: beforeDestroy, destroyed

For example, you might want to fetch data when a component mounts:

mounted() {
  // Fetch data from an API here
}
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