White page after fresh build using React Route-based code splitting

Question

The app is using react and React Route-based code splitting: https://reactjs.org/docs/code-splitting.html#route-based-code-splitting

The app is working fine. A user is on the homepage. Then I do a change in the code and build the app again.

User is clicking on a link, and he is landing on a white page. Of course, the bundle has changed, and loading the new page (thanks to React.lazy) will drop an error.

Uncaught SyntaxError: Unexpected token <

How can I prevent that and show for example: "Site has been updated, please reload" instead of a white page?

Answer 1

Solution is:

Did you know that the import(...) function that we use on lazy is just a function that returns a Promise? Which basically means that you can chain it just like any other Promise.

function retry(fn, retriesLeft = 5, interval = 1000) {
  return new Promise((resolve, reject) => {
    fn()
      .then(resolve)
      .catch((error) => {
        setTimeout(() => {
          if (retriesLeft === 1) {
            // reject('maximum retries exceeded');
            reject(error);
            return;
          }

          // Passing on "reject" is the important part
          retry(fn, retriesLeft - 1, interval).then(resolve, reject);
        }, interval);
      });
  });
}

Now we just need to apply it to our lazy import.

// Code split without retry login
const ProductList = lazy(() => import("./path/to/productlist"));

// Code split with retry login
const ProductList = lazy(() => retry(() => import("./path/to/productlist")));

If the browser fails to download the module, it'll try again 5 times with a 1 second delay between each attempt. If even after 5 tries it import it, then an error is thrown.

Thanks to Guilherme Oenning from: https://dev.to/goenning/how-to-retry-when-react-lazy-fails-mb5