mteacher/babel.config.js

// [["@vue/app", 
//         { useBuiltIns: "entry",
//         polyfills: [
//             'es6.promise',
//             'es6.symbol'
//            ]},
//     ]],
// ["@vue/app"]
module.exports = {
    presets: [["@vue/app", 
        { useBuiltIns: "entry",
        polyfills: [
            'es6.promise',
            'es6.symbol'
            ]},
    ]],
    plugins: [
        ['import', {
          libraryName: 'vant',
          libraryDirectory: 'es',
          style: name => `${name}/style/less`
        }],
        ["@babel/plugin-proposal-optional-chaining"]
    ]
}