gatsby-node.js

const path = require("path");

exports.onCreateWebpackConfig = ({ actions, stage, getConfig }) => {
  if (stage === "build-html") {
    actions.setWebpackConfig({
      externals: getConfig().externals.concat(function (
        context,
        request,
        callback
      ) {
        const regex = /^@?firebase(\/(.+))?/;
        // exclude firebase products from being bundled, so they will be loaded using require() at runtime.
        if (regex.test(request)) {
          return callback(null, "umd " + request);
        }
        callback();
      }),
    });
  }
  actions.setWebpackConfig({
    resolve: {
      alias: {
        components: path.resolve(__dirname, "src/components"),
        pages: path.resolve(__dirname, "src/pages"),
        assets: path.resolve(__dirname, "src/assets"),
        routes: path.resolve(__dirname, "src/routes"),
        context: path.resolve(__dirname, "src/context"),
      },
    },
  });
};

exports.onCreatePage = ({ page, actions }) => {
  const { createPage } = actions;
  // Make the front page match everything client side.
  // Normally your paths should be a bit more judicious.
  if (page.path === `/`) {
    page.matchPath = `/*`;
    createPage(page);
  }
};