create-react-app创建，ie11不兼容

1.安装依赖

yarn add react-app-polyfill

遇到的问题：引入依赖后，造成我的postcss-px2rem 配置失效，样式会乱掉，重新配置一下postcss-px2rem 即可（推荐postcss-px2rem-exclude）；

2. 在src/index.js的最顶部引入

import  "react-app-polyfill/ie11";
import  "react-app-polyfill/stable";

3.在packge.json文件下 browserlist 添加ie11

"browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all",
      "ie 11"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version",
      "ie 11"
    ]
  }

重启即可