Environment Configuration: Build-Time vs Runtime Config

Angular apps often run in multiple environments:
- local dev
- staging
- production

You usually need different values:
- API base URL
- analytics keys
- feature flags

## Option A: Build-time environments (simple)

Use `environment.ts` files. Angular replaces them per configuration.

Pros:
- easy
- fast

Cons:
- you must rebuild for every environment

## Option B: Runtime config (best for many environments)

Load a JSON config at runtime like:
`/assets/config.json`

Then your same build can be deployed anywhere by changing config.

### Example runtime config idea

```ts
export type AppConfig = { apiBaseUrl: string };

let config: AppConfig;

export async function loadConfig() {
  const res = await fetch('/assets/config.json');
  config = await res.json();
}

export function getConfig() {
  return config;
}
```

### Bootstrapping after config loads
You call `loadConfig()` before `bootstrapApplication`.

## When runtime config is worth it

- lots of environments (like your 80+ env style)
- same build deployed repeatedly
- DevOps wants config changes without rebuilding

> Next: Testing, unit tests vs integration tests and where Angular fits.