vue单页面模板说明文档（2）

Linter Configuration

This boilerplate uses ESLint as the linter, and uses the Standard preset with some small customizations.

If you are not happy with the default linting rules, you have several options:

1. Overwrite individual rules in .eslintrc.js. For example, you can add the following rule to enforce semicolons instead of omitting them:

   // .eslintrc.js
   "semi": [, "always"]

2. Pick a different ESLint preset when generating the project, for example eslint-config-airbnb.

3. Pick "none" for ESLint preset when generating the project and define your own rules. See ESLint documentation for more details.

   Pre-Processors

   This boilerplate has pre-configured CSS extraction for most popular CSS pre-processors including LESS, SASS, Stylus, and PostCSS. To use a pre-processor, all you need to do is installing the appropriate webpack loader for it. For example, to use SASS:

   npm install sass-loader node-sass --save-dev

   Note you also need to install node-sass because sass-loader depends on it as a peer dependency.

   Using Pre-Processors inside Components

   Once installed, you can use the pre-processors inside your *.vue components using the lang attribute on <style> tags:

   <style lang="scss">
   /* write SASS! */
   </style>

   A note on SASS syntax

   • lang="scss" corresponds to the CSS-superset syntax (with curly braces and semicolons).
   • lang="sass" corresponds to the indentation-based syntax.

   PostCSS

   Styles in *.vue files are piped through PostCSS by default, so you don't need to use a specific loader for it. You can simply add PostCSS plugins you want to use in build/webpack.base.conf.js under the vue block:

   // build/webpack.base.conf.js
   module.exports = {
     // ...
     vue: {
       postcss: [/* your plugins */]
     }
   }

   See vue-loader's related documentation for more details.

   Standalone CSS Files

   To ensure consistent extraction and processing, it is recommended to import global, standalone style files from your root App.vue component, for example:

   <!-- App.vue -->
   <style src="./styles/global.less" lang="less"></style>

   Note you should probably only do this for the styles written by yourself for your application. For existing libraries e.g. Bootstrap or Semantic UI, you can place them inside /static and reference them directly in index.html. This avoids extra build time and also is better for browser caching. (See Static Asset Handling)

   Handling Static Assets

   You will notice in the project structure we have two directories for static assets: src/assets and static/. What is the difference between them?

   Webpacked Assets

   To answer this question, we first need to understand how Webpack deals with static assets. In *.vuecomponents, all your templates and CSS are parsed by vue-html-loader and css-loader to look for asset URLs. For example, in <img src="./logo.png"> and background: url(./logo.png), "./logo.png" is a relative asset path and will be resolved by Webpack as a module dependency.

   Because logo.png is not JavaScript, when treated as a module dependency, we need to use url-loader and file-loader to process it. This boilerplate has already configured these loaders for you, so you basically get features such as filename fingerprinting and conditional base64 inlining for free, while being able to use relative/module paths without worrying about deployment.

   Since these assets may be inlined/copied/renamed during build, they are essentially part of your source code. This is why it is recommended to place Webpack-processed static assets inside /src, along side other source files. In fact, you don't even have to put them all in /src/assets: you can organize them based on the module/component using them. For example, you can put each component in its own directory, with its static assets right next to it.

   Asset Resolving Rules

   • Relative URLs, e.g. ./assets/logo.png will be interpreted as a module dependency. They will be replaced with an auto-generated URL based on your Webpack output configuration.

   • Non-prefixed URLs, e.g. assets/logo.png will be treated the same as the relative URLs and translated into ./assets/logo.png.

   • URLs prefixed with ~ are treated as a module request, similar to require('some-module/image.png'). You need to use this prefix if you want to leverage Webpack's module resolving configurations. For example if you have a resolve alias for assets, you need to use <img src="~assets/logo.png"> to ensure that alias is respected.

   • Root-relative URLs, e.g. /assets/logo.png are not processed at all.

   Getting Asset Paths in JavaScript

   In order for Webpack to return the correct asset paths, you need to use require('./relative/path/to/file.jpg'), which will get processed by file-loader and returns the resolved URL. For example:

   computed: {
     background () {
       return require('./bgs/' + this.id + '.jpg')
     }
   }

   Note the above example will include every image under ./bgs/ in the final build. This is because Webpack cannot guess which of them will be used at runtime, so it includes them all.

   "Real" Static Assets

   In comparison, files in static/ are not processed by Webpack at all: they are directly copied to their final destination as-is, with the same filename. You must reference these files using absolute paths, which is determined by joining build.assetsPublicPath and build.assetsSubDirectory in config.js.

   As an example, with the following default values:

   // config/index.js
   module.exports = {
     // ...
     build: {
       assetsPublicPath: '/',
       assetsSubDirectory: 'static'
     }
   }

   Any file placed in static/ should be referenced using the absolute URL /static/[filename]. If you change assetSubDirectory to assets, then these URLs will need to be changed to /assets/[filename].

   We will learn more about the config file in the section about backend integration.