webpack解读4（utils）

/**
 * Created by imPC on 2017/4/12.
 */
//引入path模块
var path = require('path')
//引入公共配置
var config = require('../config/index')
//分离css插件
var ExtractTextPlugin = require('extract-text-webpack-plugin')

//处理路径
exports.assetsPath = function (_path) {
    return path.posix.join(config.build.assetsSubDirectory,_path)
}

//分离css
exports.cssLoaders = function (options) {
  options = options || {}
  // generate loader string to be used with extract text plugin
  function generateLoaders (loaders) {
    var sourceLoader = loaders.map(function (loader) {
      var extraParamChar
      if (/\?/.test(loader)) {
        loader = loader.replace(/\?/, '-loader?')
        extraParamChar = '&'
      } else {
        loader = loader + '-loader'
        extraParamChar = '?'
      }
      return loader + (options.sourceMap ? extraParamChar + 'sourceMap' : '')
    }).join('!')

    if (options.extract) {
      return ExtractTextPlugin.extract({
        use: sourceLoader,
        fallback: 'vue-style-loader'
      })
    } else {
      return ['vue-style-loader', sourceLoader].join('!')
    }
  }

  // http://vuejs.github.io/vue-loader/configurations/extract-css.html
  return {
    css: generateLoaders(['css']),
    postcss: generateLoaders(['css']),
    less: generateLoaders(['css', 'less']),
    sass: generateLoaders(['css', 'sass?indentedSyntax']),
    scss: generateLoaders(['css', 'sass']),
    stylus: generateLoaders(['css', 'stylus']),
    styl: generateLoaders(['css', 'stylus'])
  }
}

//外部css的加载规则
exports.styleLoaders = function (options) {
  var output = []
  var loaders = exports.cssLoaders(options)
  for (var extension in loaders) {
    var loader = loaders[extension]
    output.push({
      test: new RegExp('\\.' + extension + '$'),
      loader: loader
    })
  }

  return output
}