ability to configure API_URL without rebuild

[legendar]

due to optimization purpose we want to do one time build for all environments (prod, stage, dev).
in multi-domain system we want to set API_URL on the app run phase.
as a proposal solution we can use separate JS file generated on backend, e.g:

// /app-config.js
window.APP_CONFIG = {
  API_URL: 'https://custom-domain.example.com/custom-sub-url/v1'
}

[romanosipenko]

Or use sed to replace placeholders with actual params on start-up

[Pareder]

Some explanation of legendar comment:

1. backend developers create custom endpoint (for example app-config.js) with such code:

window.APP_CONFIG = {
 ENV_VARIABLE: "{{ ENV_VARIABLE|setting }}"
}

2. frontend developers include this endpoint like a synchronous script BEFORE all bundle files:

<script type="text/javascript" src="./app-config.js"></script>
<script type="text/javascript" src="./bundle.js"></script>

3. frontend developers use in code window.APP_CONFIG.ENV_VARIABLE instead of process.env.ENV_VARIABLE.