Typescript : Property does not exist on type ‘object’

You probably have allProviders typed as object[] as well. And property country does not exist on object. If you don’t care about typing, you can declare both allProviders and countryProviders as Array<any>:

let countryProviders: Array<any>;
let allProviders: Array<any>;

If you do want static type checking. You can create an interface for the structure and use it:

interface Provider {
    region: string,
    country: string,
    locale: string,
    company: string
}

let countryProviders: Array<Provider>;
let allProviders: Array<Provider>;