webpack.config.js

const webpack = require("webpack")

module.exports = {
    // The configure Web pack is the place in Vue CLI 3.0 to configure the parameters of the webpack plug-in. If you set it here, it will create or override the default configuration of the webpack.
    // The meaning of webpack ProvidePlugin is to create a global variable that can be used within each module of webpack. The configuration meaning here is to create three variables'$','jQuery','window. jQuery'pointing to jQuery dependency and'Popper' pointing to popper. JS dependency.
    configureWebpack: {
        plugins: [
            new webpack.ProvidePlugin({
                $: 'jquery',
                jQuery: 'jquery',
                'window.jQuery': 'jquery',
                Popper: ['popper.js', 'default']
            })
        ]
    }
}