Merge pull request #5 from laibao101/feature/webpack5

feat: 通过特征来判断webpack5，修复语法错误

Author: yibn2008

lib/index.js

@@ -9,9 +9,7 @@ const path = require('path')
 const { RawSource } = require('webpack-sources')
 const loaderUtils = require('loader-utils')
 const cssReplace = require('./css-replace')
-const webpack = require('webpack')
 
-const webpackMajorVersion = Number(webpack.version.split('.')[0])
 const isCSS = (name) => /\.css$/.test(name)
 // const strip = (str) => str.replace(/\/$/, '')
 
@@ -66,9 +64,11 @@ class CssUrlRelativePlugin {
   }
 
   applyCompilation = (compilation) => {
+    // webpack5 新加的 hook
+    const isWebpack5 = compilation.hooks.processAssets !== undefined
     // webpack version <= 4
-    if (webpackMajorVersion <= 4) {
-      compilation.hooks.optimizeChunkAssets.tapAsync(plugin, (chunks, done) => {
+    if (!isWebpack5) {
+      compilation.hooks.optimizeChunkAssets.tapAsync(this.plugin, (chunks, done) => {
         this.fixCssUrl(compilation, chunks, done)
       })
       return;