babel
1.要安装的包
第1套包：npm i babel-core babel-loader@7 babel-plugin-transform-runtime –D(千万记得是babel-loader@7)
第2套包：npm I babel-preset-env babel-preset-stage-0 –D(注意是-零，不是字母o)
这里babel-loader一定要加版本号7，否则下载的将是最新版本8
babel版本如下所示：
{"name": "01-webpack-base","version": "1.0.0","description": "","main": "index.js","scripts": {"test": "echo \"Error: no test specified\" && exit 1","dev": "webpack-dev-server --open chrome --port 8888 --hot --host 127.0.0.1"},"keywords": [],"author": "","license": "ISC","devDependencies": {"babel-core": "^6.26.3","babel-loader": "^7.1.5","babel-plugin-transform-runtime": "^6.23.0","babel-preset-env": "^1.7.0","babel-preset-react": "^6.24.1","babel-preset-stage-0": "^6.24.1","html-webpack-plugin": "^4.3.0","webpack": "^4.43.0","webpack-cli": "^3.3.11","webpack-dev-server": "^3.11.0"},"dependencies": {"react": "^16.13.1","react-dom": "^16.13.1"}}
babel