grainCoManage/babel.config.js

module.exports = {
    // presets: [ "@babel/preset-env", "@babel/preset-react" ],
    // plugins: [ "@babel/plugin-transform-arrow-functions", "@babel/plugin-proposal-class-properties" ]
    "presets": ["@babel/preset-env", "@babel/preset-react", "mobx"],
    "plugins": [
        "@babel/plugin-proposal-object-rest-spread",
        "@babel/plugin-transform-runtime"
    ]
}