Vuepress Markdown Variable substitution

config.js

// inside config.js extend webpack so that `__var_name__` is replaced with value of `config[var_name]`
// relies on npm install string-replace-loader
{ 
  configureWebpack(config) {
    config.resolve.alias["@"] = path.join(__dirname, "/theme");
    config.resolve.alias["~"] = path.join(__dirname, "/public");
    if (process.env.NODE_ENV === "production") {
      const mappings = Object.keys(config).map(key => {
        return { search: `__${key}__`, replace: config[key] }
      })
      console.log(mappings)
      config.module.rules.push({
        test: /\.*/,
        loader: "string-replace-loader",
        options: {
          multiple: mappings
        }
      });
    }
  }
}