Change type of an array in typescript

If you want to make it work for any Object I would use the javascript Object.keys which will return you all the object's own property names , read more about it here

Then create an function that will map any class object.

let clientArray : Client[] = [ 
  new Client(24, 'Kobe'), 
  new Client(23, 'Lebron James'),
  new Client(1, 'Zion Williams')
]
let productsArray : Product[] = [ 
  new Product(24, 'Sneakers'), 
  new Product(23, 'Bling),
]

// use this function to map any class to to a simple object.
function mapToSimple(client){ 
    let keys = Object.keys(client)
    let result = {}
    keys.forEach((key) => {
        result[key] = client[key];
    })
    return result;
};

let results = clientArray.map(mapToSimple)
let anotherResults = productsArray.map(mapToSimple)
console.log(results);
console.log(anotherResults);

Mapping an array of Clients to an array of Client attributes needs the provided function to the map method to pick out the attributes. e.g.

Say there is the following Client class:

class Client {
   clientId: Number;
   clientName: string;

   constructor(clientId: Number, clientName: string) {
      this.clientId = clientId;
      this.clientName = clientName;
   }
}

And there is an initial array of Client instances.

const clientInstances  : Client[] = [ 
  new Client(1, 'Raymond'), 
  new Client(2, 'Damond') 
]

console.log(clientInstances);
// [ Client { clientId: 1, clientName: 'Raymond' },
//   Client { clientId: 2, clientName: 'Damond' } ]

The function provided to the map method is passed each client instance and a new object returned with the client attribute value set for the related key.

interface IClient { 
    clientName: string;
    clientId: Number; 
}

const clientObjects : IClient[] = clientInstances.map(
  client => (
    { clientName: client.clientName, clientId: client.clientId }
  )
)

console.log(clientObjects);
// [ { clientName: 'Raymond', clientId: '1' },
//   { clientName: 'Damond', clientId: '2' } ]

• For a Pure TS solution where all you care about is the type just Pick it

class Client {
   clientId: number;
   clientName: string;

   constructor(clientId: number, clientName: string) {
      this.clientId = clientId;
      this.clientName = clientName;
   }
}

type ClientArray = Client[];
type JustValues = Pick<Client, 'clientId' | 'clientName'>[]

If you know you want to include all of the values from the Class/interface you can do

type JustValues = Pick<Client, keyof Client>[]

TSPlayground