CLIを使用せずに単一ファイルコンポーネントを使用してVue.jsアプリを作成する方法。

この記事では、Vueの単一ファイルコンポーネント(SFC)とノードパッケージマネージャー(NPM)について理解しておくと役立ちます。

フレームワークのコマンドラインインターフェイス(CLI)は、プロジェクトの足場を作るための推奨される方法です。これは、ファイル、フォルダー、および構成の開始点を提供します。この足場は、開発および構築プロセスも提供します。開発プロセスは、プロジェクトの編集時に発生する更新を確認する方法を提供します。ビルドプロセスでは、本番環境で使用するファイルの最終バージョンが作成されます。

Vue.js(「Vue」)のインストールと実行は、Vueコンテンツ配信ネットワーク(CDN)を指すスクリプトタグを使用して実行できます。ビルドや開発プロセスは必要ありません。ただし、Vue単一ファイルコンポーネント(SFC)を使用する場合は、それらのファイルをブラウザーが理解できるものに変換する必要があります。ファイルは、ハイパーテキストマークアップ言語(HTML)、カスケードスタイルシート(CSS)、およびJavaScript(JS)に変換する必要があります。この場合、開発およびビルドプロセスを使用する必要があります。

Vue CLIを使用してプロジェクトの足場を作り、開発とビルドのプロセスを提供する代わりに、プロジェクトを最初からビルドします。Webpackを使用して独自の開発およびビルドプロセスを作成します。

Webpackとは何ですか?

Webpackはモジュールバンドラーです。複数のファイルのコードを1つにマージします。Webpackの前に、ユーザーは各JavaScriptファイルのスクリプトタグを含めていました。ブラウザはES6モジュールを徐々にサポートしていますが、モジュラーコードを構築するための好ましい方法は引き続きWebpackです。

モジュールバンドラーであることに加えて、Webpackはコードを変換することもできます。たとえば、Webpackは最新のJavaScript(ECMAScript 6+)を使用してECMAScript 5に変換できます。Webpackはコード自体をバンドルしますが、ローダーとプラグインを使用してコードを変換します。ローダーとプラグインをWebpackのアドオンと考えてください。

WebpackとVue

単一ファイルコンポーネントを使用すると、コンポーネント全体(構造、スタイル、および機能)を1つのファイルに構築できます。また、ほとんどのコードエディタは、これらのSFCの構文の強調表示とリンティングを提供します。

ファイルが.vueで終わっていることに注意してください。ブラウザはその拡張機能をどうするかを知りません。Webpackは、ローダーとプラグインを使用して、このファイルをブラウザーが使用できるHTML、CSS、およびJSに変換します。

プロジェクト:単一ファイルコンポーネントを使用してHello WorldVueアプリケーションを構築します。

ステップ1:プロジェクト構造を作成する

最も基本的なVueプロジェクトには、HTML、JavaScript、およびVueファイル(.vueで終わるファイル)が含まれます。これらのファイルをというフォルダに配置しますsrcソースフォルダーは、作成中のコードをWebpackが最終的にビルドするコードから分離するのに役立ちます。

Webpackを使用するため、Webpack構成ファイルが必要です。

さらに、Babelというコンパイラを使用します。Babelを使用すると、ES6コードを記述してES5にコンパイルできます。Babelは、Webpackの「アドオン機能」の1つです。Babelには構成ファイルも必要です。

最後に、NPMを使用しているため、node_modulesフォルダーpackage.jsonファイルもあります。これらは、プロジェクトをNPMプロジェクトとして初期化し、依存関係のインストールを開始すると自動的に作成されます。

開始するには、という名前のフォルダを作成しますhello-world。コマンドラインから、そのディレクトリに移動してを実行しnpm initます。画面の指示に従ってプロジェクトを作成します。次に、上記のように残りのフォルダー(を除くnode_modulesを作成します。プロジェクト構造は次のようになります。

ステップ2:依存関係をインストールする

使用している依存関係の概要は次のとおりです。

vue:JavaScriptフレームワーク

vue-loaderおよびvue-template-compiler:VueファイルをJavaScriptに変換するために使用されます。

webpack:コードをいくつかの変換に渡して1つのファイルにバンドルできるようにするツール。

webpack-cli: Webpackコマンドを実行するために必要です。

webpack-dev-server:小さなプロジェクトには必要ありませんが(HTTPリクエストを行わないため)、開発サーバーからプロジェクトを「提供」します。

babel-loader:ES6コードをES5に変換します。(次の2つの依存関係からの助けが必要です。)

@babel/core and @babel/preset-env: Babel by itself doesn’t do anything to your code. These two “add-ons” will allow us to transform our ES6 code into ES5 code.

css-loader: Takes the CSS we write in our .vuefiles or any CSS we might import into any of our JavaScript files and resolve the path to those files. In other words, figure out where the CSS is. This is another loader that by itself won’t do much. We need the next loader to actually do something with the CSS.

vue-style-loader: Take the CSS we got from our css-loader and inject it into our HTML file. This will create and inject a style tag in the head of our HTML document.

html-webpack-plugin: Take our index.html and inject our bundled JavaScript file in the head. Then, copy this file into the distfolder.

rimraf: Allows us, from the command line, to delete files. This will come in handy when we build our project multiple times. We will use this to delete any old builds.

Let’s install these dependencies now. From the command line, run:

npm install vue vue-loader vue-template-compiler webpack webpack-cli webpack-dev-server babel-loader @babel/core @babel/preset-env css-loader vue-style-loader html-webpack-plugin rimraf -D

Note: The “-D” at the end marks each dependency as a development dependency in our package.json. We are bundling all dependencies in one file, so, for our small project, we have no production dependencies.

Step 3: Create the files (Except for our Webpack configuration file).

 {{ message }} export default { data() { return { message: 'Hello World', }; }, };   #app { font-size: 18px; font-family: 'Roboto', sans-serif; color: blue; } 
  Vue Hello World 
import Vue from 'vue'; import App from './App.vue'; new Vue({ el: '#app', render: h => h(App), });
module.exports = { presets: ['@babel/preset-env'], }

Up to this point, nothing should look too foreign. I’ve kept each file very basic. I’ve only added minimal CSS and JS to see our workflow in action.

Step 4: Instructing Webpack what to do

All the configuration Webpack needs access to is now present. We need to do two final things: Tell Webpack what to do and run Webpack.

Below is the Webpack configuration file (webpack.config.js). Create this file in the projects root directory. Line-by-line we’ll discuss what is occurring.

const HtmlWebpackPlugin = require('html-webpack-plugin'); const VueLoaderPlugin = require('vue-loader/lib/plugin'); module.exports = { entry: './src/main.js', module: { rules: [ { test: /\.js$/, use: 'babel-loader' }, { test: /\.vue$/, use: 'vue-loader' }, { test: /\.css$/, use: ['vue-style-loader', 'css-loader']}, ] }, plugins: [ new HtmlWebpackPlugin({ template: './src/index.html', }), new VueLoaderPlugin(), ] };

Lines 1 and 2: We are importing the two plugins we use below. Notice, our loaders don’t normally need to be imported, just our plugins. And in our case, thevue-loader (which we use in line 9) also needs a plugin to work (however, Babel, for example, does not).

Line 4: We export our configuration as an object. This gives us access to it when we run the Webpack commands.

Line 5: This is our entry module. Webpack needs a place to start. It looks in our main.js file and then starts to comb through our code from that point.

Line 6 and 7: This is the module object. Here, we primarily pass in an array of rules. Each rule tells Webpack how to handle certain files. So, while Webpack uses the entry point of main.js to start combing through our code, it uses the rules to transform our code.

Line 8 (rule): This rule instructs Webpack to use the babel-loader on any files which end with .js. Remember, Babel will transform ES6+ to ES5.

Line 9 (rule): This rule instructs Webpack to use vue-loader(and don’t forget the associated plugin on line 17) to transform our .vue files into JavaScript.

Line 10 (rule): Sometimes we want to pass a file through two loaders. Counterintuitively, Webpack will pass the file from right to left instead of left to right. Here we are using two loaders and saying to Webpack: “get my CSS from my Vue file or any JavaScript files(css-loader) and inject it into my HTML as a style tag (vue-style-loader).

Lines 11 and 12: Close out our rules array and module object.

Lines 13: Create a plugins array. Here we will add the two plugins we need.

Line: 14 -16 (plugin): The HtmlWebpackPlugin takes the location of our index.html file and adds our bundled JavaScript file to it via a script tag. This plugin will also copy the HTML file to our distribution folder when we build our project.

Line 17 (plugin): The VueLoaderPlugin works with our vue-loader to parse our .vue files.

Line 18: Close out the plugins array.

Line 19: Close out the Webpack object that we are exporting.

Step 5: Setting up our package.json file so we can run Webpack

Our configuration is complete, now we want to see our application. Ideally, as we make changes to our application, the browser would update automatically. This is possible with webpack-dev-server.

Delete the test script in our package.json file, and replace it with a script to serve our application:

 { "name": "hello-world", "version": "1.0.0", "description": "", "main": "main.js", "scripts": { "serve": "webpack-dev-server --mode development" }, "author": "", "license": "ISC", "devDependencies": { "@babel/core": "^7.1.6", "@babel/preset-env": "^7.1.6", "babel-loader": "^8.0.4", "css-loader": "^1.0.1", "html-webpack-plugin": "^3.2.0", "rimraf": "^2.6.2", "vue": "^2.5.17", "vue-loader": "^15.4.2", "vue-style-loader": "^4.1.2", "vue-template-compiler": "^2.5.17", "webpack": "^4.26.0", "webpack-cli": "^3.1.2", "webpack-dev-server": "^3.1.10" }, "dependencies": {} }

The name of this command is your choice. I chose to call mine serve since we will be serving our application.

From our terminal or command line, we can run npm run serve and that in turn will run webpack-dev-server --mode development .

The --mode development is what’s called a flag or option. We haven’t talked about this, but it essentially instructs Webpack that you are in development mode. We can also pass in --mode production which we will do when we build our project. These aren’t necessarily required for Webpack to work. Without these, you will get a warning message telling you to provide a mode when you run Webpack .

I say “necessarily required” because Webpack will minimize our code in production mode but not in development. So, don’t think those commands don’t do anything–they do.

Let’s run npm run serve and see what happens.

When we run npm run serve we get some output in our terminal. And, if everything goes well:

And if we scroll up a bit:

Point your browser to //localhost:8080. You will see your Blue Hello World message in Roboto font.

Now, let’s update the project and change the message to Hello Universe. Notice that the webpage refreshes automatically. That’s great, right? Can you think of a downside?

Let’s change the application just a bit and include an input which we will bind a variable to (with v-model). We will output the variable in an

tag below the input. I’ve also updated the styling section to style the message now. Our App.vuefile should look like this:

{{ message }}

export default { data() { return { message: 'Hello world!', }; }, }; .message { font-size: 18px; font-family: 'Roboto', sans-serif; color: blue; }

When we serve our application, we will have an input with a message of Hello World below it. The input is bound to the message variable, so as we type, we change the

content. Go ahead, type into the input to change the

content.

Now go back to your editor, and below the

tag, add the following:

Some Other Message

Save your App.vue and watch what happens.

The h2 we just updated by typing in our input reverted back to Hello World. This is because the browser actually refreshes, and the script tag and page are loaded again. In other words, we were not able to maintain the state of our application. This may not seem like a big deal, but as you are testing your application and adding data to it, it will be frustrating if your app “resets” every time. Fortunately, Webpack offers us a solution called Hot Module Replacement.

The hot module replacement is a plugin provided by Webpack itself. Up until this point, we have not used the Webpack object itself in our configuration file. However, we will now import Webpack so we can access the plugin.

In addition to the plugin, we will pass one additional option to Webpack, the devServer option. In that option, we will set hot to true. Also, we will make an (optional) update to our build workflow: We will open the browser window automatically when we run npm run serve. We do this by setting open to true which is also inside the devServer option.

const HtmlWebpackPlugin = require('html-webpack-plugin'); const VueLoaderPlugin = require('vue-loader/lib/plugin'); const webpack = require('webpack'); module.exports = { entry: './src/main.js', module: { rules: [ { test: /\.js$/, use: 'babel-loader' }, { test: /\.vue$/, use: 'vue-loader' }, { test: /\.css$/, use: ['vue-style-loader', 'css-loader']}, ] }, devServer: { open: true, hot: true, }, plugins: [ new HtmlWebpackPlugin({ template: './src/index.html', }), new VueLoaderPlugin(), new webpack.HotModuleReplacementPlugin(), ] };

Notice that we’ve imported Webpack so we could access the hotModuleReplacementPlugin. We’ve added that to the plugins array, and then told Webpack to use it with hot: true. We open the browser window automatically when we serve the application with open: true.

Run npm run serve:

The browser window should open, and if you open your dev tools, you should notice a slight change in the output. It now tells us hot module replacement is enabled. Let’s type in our input to change the

content. Then, change theh3 tag to read: One More Message.

Save your file and notice what happens.

The browser doesn't refresh, but our

change is reflected! The message we typed in the input remains, but the h3 updates. This allows our application to keep it’s state while we edit it.

Step 7: Building our project

So far, we’ve served our application. But, what if we want to build our application so we can distribute it?

If you noticed, when we serve our application, no files are created. Webpack creates a version of these files that only exist in temporary memory. If we want to distribute our Hello World app to our client, we need to build the project.

This is very simple. Just like before, we will create a script in our package.json file to tell Webpack to build our project. We will use webpack as the command instead of webpack-dev-server. We will pass in the --mode production flag as well.

We will also use the rimraf package first to delete any previous builds we may have. We do this simply by rimraf dist.

dist is the folder Webpack will automatically create when it builds our project. “Dist” is short for distribution–i.e. we are “distributing” our applications code.

The rimraf dist command is telling therimraf package to delete the dist directory. Make sure you don’t rimraf src by accident!

Webpack also offers a plugin that will accomplish this cleaning process called clean-webpack-plugin. I chose dist show an alternative way.

Our package.json file should look like this:

{ "name": "hello-world", "version": "1.0.0", "description": "", "main": "main.js", "scripts": { "clean": "rimraf dist", "build": "npm run clean && webpack --mode production", "serve": "webpack-dev-server --mode development" }, "author": "", "license": "ISC", "devDependencies": { "@babel/core": "^7.1.6", "@babel/preset-env": "^7.1.6", "babel-loader": "^8.0.4", "css-loader": "^1.0.1", "html-webpack-plugin": "^3.2.0", "rimraf": "^2.6.2", "vue": "^2.5.17", "vue-loader": "^15.4.2", "vue-style-loader": "^4.1.2", "vue-template-compiler": "^2.5.17", "webpack": "^4.26.0", "webpack-cli": "^3.1.2", "webpack-dev-server": "^3.1.10" }, "dependencies": {} }

There are three things to notice:

  1. I’ve created a separate clean script so we can run it independently of our build script.
  2. npm run build will call the independent clean script we’ve created.
  3. I have && between npm run clean and webpack. This instruction says: “run npm run clean first, then run webpack”.

Let’s build the project.

npm run build

Webpack creates a dist directory, and our code is inside. Since our code makes no HTTP requests, we can simply open our index.html file in our browser and it will work as expected.

If we had code that was making HTTP requests, we would run into some cross-origin errors as we made those requests. We would need to run that project from a server for it to work.

Let’s examine the index.html that Webpack created in the browser and the code editor.

If we open it in our editor or take a look at the source code in our dev tools you will see Webpack injected the script tag. In our editor though, you won’t see the styles because the style tag is injected dynamically at runtime with JavaScript!

Also, notice our development console information is no longer present. This is because we passed the --production flag to Webpack.

Conclusion

Understanding the build process behind the frameworks you use will help you to better understand the framework itself. Take some time to try to build an Angular, React or another Vue Project without the use of the respective CLIs. Or, just build a basic three-file site (index.html, styles.css, and app.js), but use Webpack to serve and build a production version.

Thanks for reading!

woz