runtime-config-loader

Angular Runtime Configuration Loader

Most applications require certain configuration values that can be changed at runtime of the app. The environment.ts files in an Angular application technically work for setting configuration values in an app, but those are buildtime configuration values. This means that they are set when the application is built, and can't be changed unless the app is built again.

Overview

This library provides an easy way to load a JSON file with configuration values or make an HTTP GET call to an API endpoint that returns those values. You can then use that configuration throughout the application. The default location of the JSON file is in the assets folder, at ./assets/config.json. When the service loads the file, it stores that configuration object in a local variable which can be accessed via the getConfig() and getConfigObjectKey(key: string) methods. getConfig returns the entire configuration object; getConfigObjectKey(key: string) returns part of the configuration object, namely the part defined by the key passed in. In some cases, the config.json is not finished loading before other modules/services are, so the above methods will return null. If that is the case, subscribe to the configSubject and access the configuration object that way.

How to Implement

In your app.module.ts file, add the following to the @NgModule decorator:

imports: [..., RuntimeConfigLoaderModule, ...],

That's it; it's that simple. In the RuntimeConfigLoaderModule, the APP_INITIALIZER token is used to run a function which loads the configuration from a file or an API endpoint that can be used throughout the application.

If you implement the library exactly as it is above, the configuration file needs to be in the ./assets/config.json location as mentioned above. If you'd like to load the file from a different location, provide that location in the .forRoot() method when importing the RuntimeConfigLoaderModule:

imports: [
  ...,
  RuntimeConfigLoaderModule.forRoot(
    { configUrl: './path/to/config/config.json' }
  ),
  ...]

Make sure that the path you provide here is accessible by the Angular application, meaning that the file is somewhere the app can load it. In my opinion, the assets folder is the easiest place to work from.