Blog: A Guide To Vue CLI, Project Setup, Computed Properties, And Watchers

Introduction

Learn how to set up a Vue.js project with Vue CLI and understand key concepts like computed properties and watchers in this beginner-friendly guide. Perfect for Vue.js enthusiasts and those preparing for interviews!

Imagine you’re building a really cool Lego house, but before you can start, you need all your Lego pieces organized and ready. Vue CLI (Command Line Interface) is like a special box that helps you organize your Lego pieces, so when you’re ready to build your Vue.js app, everything is easy to find and put together.

In this blog, we’ll walk you through two very important concepts in Vue.js: Vue CLI and Project Setup and Computed Properties and Watchers. We’ll explain them in simple terms, and by the end, you’ll be able to set up your own Vue.js project and use computed properties and watchers to make your app smarter!

1. Vue CLI and Project Setup

What is Vue CLI?

Think of Vue CLI as a magical toolkit that makes building Vue.js apps super easy. When you’re making a project, you need a lot of things like files, settings, and tools. Vue CLI helps you create and organize these things quickly. It’s like using a template to start your Lego house rather than figuring everything out from scratch.

Setting up a Vue.js Project with Vue CLI

Here’s how you can use Vue CLI to set up a Vue.js project:

Install Vue CLI:
First, you need to install Vue CLI. This is like getting your special box of Lego pieces. To install it, you need Node.js installed on your computer. Once you have Node.js, you can install Vue CLI by typing this command in your terminal: npm install -g @vue/cli
Create a New Project:
After installing Vue CLI, you can create a new project using the following command: vue create my-project Replace my-project with your project name. Vue CLI will ask you a few questions about how you want your project to be set up, such as using Vue 3 or Vue 2, adding extra features, etc. You can pick the default options if you’re not sure.
Start Your Project:
After your project is created, go to the project folder and run the app: cd my-project npm run serve This will start your Vue.js app, and you can see it running in the browser!

2. Computed Properties and Watchers in Vue.js

Now, let’s talk about computed properties and watchers, two features that help your Vue.js app become super smart and reactive!

What Are Computed Properties?

Imagine you’re building a Lego car, and you want to calculate how many wheels the car will have based on how many parts you’ve added. Instead of doing the math manually every time, you can set up a rule that says, “If I add 4 parts to the car, then it will automatically have 4 wheels.”

In Vue.js, computed properties work like this rule. They automatically calculate values based on data changes, and they only update when necessary.

For example, if you have a price and taxRate in your app, you can create a computed property for the total price:

data() {
  return {
    price: 100,
    taxRate: 0.1
  }
},
computed: {
  totalPrice() {
    return this.price + this.price * this.taxRate;
  }
}

Whenever price or taxRate changes, the totalPrice will automatically update, just like magic!

What Are Watchers?

Now, let’s say you want to keep track of when the price of your Lego car changes. You don’t want to calculate the total every time, but you do want to know when the price changes.

This is where watchers come in. They let you “watch” certain data for changes and then do something when those changes happen. It’s like having a helper who alerts you when the Lego car price changes.

Here’s an example of how you can set up a watcher in Vue.js:

watch: {
  price(newValue, oldValue) {
    console.log(`Price changed from ${oldValue} to ${newValue}`);
  }
}

In this example, every time the price changes, the watcher will log a message showing the old and new values.

Interview Questions and Answers

Here are some interview questions and answers based on Vue CLI and Project Setup, as well as Computed Properties and Watchers:

Q1: What is Vue CLI, and why is it useful?
A1: Vue CLI is a command-line tool that helps you quickly set up and manage Vue.js projects. It provides a ready-to-use setup with all the necessary configurations, like Webpack, Babel, and ESLint, to streamline development.

Q2: How do you create a new Vue.js project using Vue CLI?
A2: To create a new Vue.js project, you first need to install Vue CLI globally by running npm install -g @vue/cli. Then, you can create a new project using the command vue create my-project and follow the prompts to set up your project.

Q3: What are computed properties in Vue.js?
A3: Computed properties are reactive properties in Vue.js that automatically calculate values based on other data. They are cached and only recomputed when their dependencies change, making them efficient for performance.

Q4: What is the difference between computed properties and methods in Vue.js?
A4: Computed properties are cached and only re-evaluated when their dependencies change, whereas methods are evaluated every time they are called, even if the data hasn’t changed.

Q5: What are watchers used for in Vue.js?
A5: Watchers in Vue.js allow you to react to changes in specific data properties. They are useful when you need to perform an action or side effect in response to a data change, such as making an API call or logging a message.

Q6: How can you watch for changes to an object in Vue.js?
A6: You can watch an object or array by specifying the object in the watch option. For example:

watch: {
  'user.name': function(newValue, oldValue) {
    console.log(`User name changed from ${oldValue} to ${newValue}`);
  }
}

Companies That Have Asked About Vue CLI and Computed Properties in Interviews

Several companies have asked about Vue.js, including Vue CLI setup, computed properties, and watchers during technical interviews for frontend development roles. Some of these companies include:

Tata Consultancy Services (TCS)
Capgemini
Accenture
Cognizant
Infosys
Wipro
CureMetrix
Zscaler
Zoho Corporation

These companies often look for developers who are comfortable with modern JavaScript frameworks and can efficiently use Vue.js to build scalable, reactive applications.

Conclusion

Now you’re ready to get started with Vue.js using Vue CLI, and you understand how computed properties and watchers can make your app smarter and more reactive. Whether you’re setting up your project with Vue CLI or using computed properties to dynamically calculate values, Vue.js makes it easy to create amazing, interactive web apps. Happy coding! 🚀

Feel free to explore these topics to deepen your knowledge and expertise in Vue.js. The more you practice and experiment, the better you’ll become at building powerful and efficient web applications!

Blog: A Guide to Vue CLI, Project Setup, Computed Properties, and Watchers