¿ How to check admin role? : I am looking the best way to check admin rolewith component in angular.

I have the following code in component
 

  

     checkIfIsAdmin(): any {
            let user_string = localStorage.getItem("currentUser");
            if (!isNullOrUndefined([user_string])) {
                console.log(user_string);
                return true;
            } else {
              return null;
            }
          }

I need to check the ROLE_ADMIN that I receive with the following format,

    {"longId":4,"name":"bbb","email":"bbb@gmail.com","userName":"bbb","token":"eyJhbGciOiJIUzUxMiJ9.eyJzdWIiOiI0IiwiaWF0IjoxNTU5NDk0NTczLCJleHAiOjE1NTk0OTQ4NzN9.XmSHywZv09b4BR9-NxyCTVPF33pLsk3QtTEXQMQF4YHW7i27Ghj2Uh3WZAegpG4rdSImKcm1wMgJsPLpHcTyew","roles":["ROLE_USER","ROLE_ADMIN"]}

I don't know how to iterate roles inside if condition , could anyone help to me ?