Syntax Error: Error: PostCSS received undefined instead of CSS string （已解决）

PostCSS received undefined instead of CSS string （已解决）"/>

Syntax Error: Error: PostCSS received undefined instead of CSS string （已解决）

错误版本

"node-sass": "^5.0.0"
"sass-loader": "^10.1.0"

解决办法如下：

这是因为node-sass 和 sass-loader版本不适配导致，请安装如下版本，并且运行如下命令：

"node-sass": "^4.14.1"
"sass-loader": "^8.0.0"

npm uninstall sass-loader

npm uninstall node-sass

npm install node-sass@4.14.1

npm install sass-loader@8.0.0