Running and building a Vue app

Introduction

Running a Vue app lets you see your work in a browser while building prepares your app for sharing with others.

You want to test your Vue app on your computer during development.

You need to create a version of your app that loads fast on the internet.

You want to check how your app looks and works on different devices.

You are ready to share your app with friends or users online.

Syntax

Vue

npm run dev
npm run build
npm run preview

npm run dev starts a local server to run your app during development.

npm run build creates optimized files for production use.

npm run preview starts a local server to preview the built app.

Examples

This command runs your Vue app locally so you can see changes live.

Vue

npm run dev

This command prepares your app files for fast loading on the web.

Vue

npm run build

This command lets you preview the built app locally before sharing.

Vue

npm run preview

Sample Program

This example shows the commands you type to run and build your Vue app step-by-step.

Vue

/* Steps to run and build a Vue app */

// 1. Open terminal in your Vue project folder
// 2. Run the development server:
npm run dev

// 3. After finishing development, build the app:
npm run build

// 4. Preview the built app locally:
npm run preview

Important Notes

Make sure you have Node.js and npm installed before running these commands.

Use a modern browser to open the local URL shown after running npm run dev.

The dist folder contains your built app ready to upload to a web server.

Summary

Use npm run dev to run your Vue app locally during development.

Use npm run build to create optimized files for production.

Use npm run preview to check the built app before sharing.

Practice

1. Which command do you use to start your Vue app locally during development?

easy

A. npm run preview

B. npm run build

C. npm run dev

D. npm start

Solution

1. Step 1: Understand the purpose of each command

   npm run dev is used to run the app locally for development, npm run build creates production files, and npm run preview previews the production build.

2. Step 2: Match the command to running locally

   Since running locally during development means seeing live changes, npm run dev is the correct command.

3. Final Answer:

   npm run dev -> Option C

4. Quick Check:

   Run locally = npm run dev [OK]

Hint: Run locally during development with npm run dev [OK]

Common Mistakes:

• Confusing build with dev command
• Using npm start instead of npm run dev
• Trying to preview before building

2. Which of the following is the correct command to create optimized production files for a Vue app?

easy

A. npm run dev

B. npm run build

C. npm run start

D. npm run preview

Solution

1. Step 1: Identify the command for production build

   npm run build is the standard command to create optimized files for production in Vue apps.

2. Step 2: Eliminate other options

   npm run dev runs the app locally, npm run preview previews the build, and npm run start is not a default Vue command.

3. Final Answer:

   npm run build -> Option B

4. Quick Check:

   Build production = npm run build [OK]

Hint: Build production files with npm run build [OK]

Common Mistakes:

• Using npm run dev to build
• Typing npm run start which is not default
• Confusing preview with build

3. What will happen if you run npm run preview after building your Vue app?

medium

A. It starts a local server to preview the production build

B. It rebuilds the app for development

C. It deletes the build folder

D. It runs the app in development mode

Solution

1. Step 1: Understand the purpose of npm run preview

   This command serves the production build locally so you can check how the optimized app works before sharing.

2. Step 2: Compare with other options

   It does not rebuild or delete files, nor does it run development mode. It only previews the built app.

3. Final Answer:

   It starts a local server to preview the production build -> Option A

4. Quick Check:

   Preview = local server for production build [OK]

Hint: Preview runs a local server for the built app [OK]

Common Mistakes:

• Thinking preview rebuilds the app
• Confusing preview with dev mode
• Assuming preview deletes files

4. You ran npm run build but your dist folder is empty. What is the most likely cause?

medium

A. You forgot to install dependencies with npm install

B. You ran npm run dev instead of build

C. You ran npm run preview before building

D. Your package.json has no build script defined

Solution

1. Step 1: Check if build script exists

   If npm run build runs but produces no files, likely the build script is missing or misconfigured in package.json.

2. Step 2: Rule out other causes

   Missing dependencies cause errors, not empty folders. Running dev or preview does not create build files. So missing build script is the main cause.

3. Final Answer:

   Your package.json has no build script defined -> Option D

4. Quick Check:

   Empty build folder = missing build script [OK]

Hint: Check package.json for build script if dist is empty [OK]

Common Mistakes:

• Assuming npm install fixes empty dist
• Confusing dev and build commands
• Trying preview before building

5. You want to share your Vue app with a friend but first want to check the production version locally. Which sequence of commands should you run?

hard

A. npm run build, then npm run preview

B. npm run dev, then npm run preview

C. npm run preview, then npm run build

D. npm run build, then npm run dev

Solution

1. Step 1: Build the production files first

   You must run npm run build to create optimized files for production.

2. Step 2: Preview the production build locally

   After building, run npm run preview to start a local server and check the production version before sharing.

3. Final Answer:

   npm run build, then npm run preview -> Option A

4. Quick Check:

   Build then preview to check production [OK]

Hint: Build first, then preview to check production locally [OK]

Common Mistakes:

• Previewing before building
• Running dev instead of preview for production check
• Running preview then build in wrong order