How should I configure create-react-app to serve app from subdirectory?

Question

I have classic web application rendered on server. I want to create admin panel as single page application in React. I want to server admin panel from https://smyapp.example.com/admin/. I try to use create-react-app but it assumes that i serve SPA from root URL. How should I configure create-react-app to serve app from "admin" subdirectory? In documentation I found "homepage" property but if I properly understand it requires complete url. I can't give complete url because my app is deployed in few environments.

Answer 1

In addition to your requirements, I am adding mine:

• It should be done by CD, through an env variable.
• If I need to rename the subdirectory, I should only have to change the env variable.
• It should work with react-router.
• It should work with scss (sass) and html.
• Everything should work normally in dev mode (npm start).

I also had to implement it in Angular2+ project not long ago, I found it harder to implement in React then in Angular2+ where you are good to go with ng build --base-href /<project_name>/. source

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Short version

1. Before building, set PUBLIC_URL env variable to the value of your subdirectory, let use /subdir for example. You can also put this variable into your .env.production (in case you do not have that file you can check the doc)
2. In public/index.html add the base element bellow, this is for static files like images.

<base href="%PUBLIC_URL%/">

3. Also in public/index.html, if you have custom link element, make sure theyre are prefixed with %PUBLIC_URL% (like manifest.json and favicon.ico href).
4. If you use BrowserRouter, you can add basename prop:

<BrowserRouter basename={process.env.PUBLIC_URL} />

5. If you use Router instead, because you need access to history.push method, to programmatically change page, do the following:

// history.tsx
import {createBrowserHistory} from 'history';

export default createBrowserHistory({ basename: process.env.PUBLIC_URL });

<!-- Where your router is, for me, App.tsx -->
<Router history={history}>
  ...
</Router>

6. Use relative links inside your elements

<!-- "./assets/quotes.png" is also ok, but "/assets/quotes.png" is not -->
<img src="assets/quotes.png" alt="" />

7. Move your background-image links from scss to jsx/tsx files (note that you may not need to do that if you use css files):

/*remove that*/
background-image: url('/assets/background-form.jpg');

<section style={{backgroundImage: `url('assets/background-form.jpg')`}}>
...

You should be done.

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Additional informations

I preferred to use PUBLIC_URL instead of homepage in package.json because I want to use env variable set on gitlab to set the subdir. Relevant resources about the subject:

• https://create-react-app.dev/docs/deployment/#building-for-relative-paths
• https://create-react-app.dev/docs/advanced-configuration/
• https://github.com/facebook/create-react-app/issues/998

PUBLIC_URL override homepage, and PUBLIC_URL also take the domain name, if you provide one. If you set only homepage, PUBLIC_URL will be set to the value of homepage.

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If you do not want to use a base element in your index.html (I would not know why), you will need to append process.env.PUBLIC_URL to every link yourself. Note that if you have react-router with a base element, but have not set basename prop, you will get a warning.

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Sass won't compile with an incorrect relative path. It also won't compile with correct relative path to your ../public/assets folder, because of ModuleScopePlugin restrictions, you can avoid the restriction by moving your image inside the src folder, I haven't tried that.

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There seem to be no way of testing relative path in development mode (npm start). see comment

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Finnaly, theses stackoverflow link have related issues:

• Can I set a base route in react-router
• Setting base href using Environment variables

Answer 2

For create-react-app v2 and react-router v4, I used the following combo to serve a production (staging, uat, etc) app under "/app":

package.json:

"homepage": "/app"

Then in the app entry point:

 <BrowserRouter basename={process.env.PUBLIC_URL}>
  {/* other components */}
 </BrowserRouter>

And everything "just works" across both local-dev and deployed environments. HTH!