Add your variable and make sure that you configure each environment.

// ./public_html/src/environments/environment.ts or environment.prod.ts
export const environment = {
    production: false,
    apiUrl: 'https://example.apiurl.dev'
};

Then import the environment variables and use where necessary.

// ./public_html/src/app/example.ts
import {environment} from '../environments/environment';

export class Example {
    public envOptions = {
        apiUrl : environment.apiUrl
        // ...
    }
    // ...
}