Guids are usually represented as strings in Javascript, so the simplest way to represent the GUID is as a string. Usually when serialization to JSON occurs it is represented as a string, so using a string will ensure compatibility with data from the server.
To make the GUID different from a simple string, you could use branded types:
type GUID = string & { isGuid: true};
function guid(guid: string) : GUID {
return guid as GUID; // maybe add validation that the parameter is an actual guid ?
}
export interface Product {
id: GUID;
productName: string;
price: number;
level: number;
}
declare let p: Product;
p.id = "" // error
p.id = guid("guid data"); // ok
p.id.split('-') // we have access to string methods
This article has a bit more of a discussion on branded types. Also the typescript compiler uses branded types for paths which is similar to this use case.