Acessing type as object or Array in Typescript

Question

I am new to typescript.

I have a class Like this

class Document {
  constructor (data, id) {
    this.data = data
    this.id = id
  }
}

Here I know that Id is going to be String but data is going to be either object or array .

Can someone help me in figuring out what is going to be the interface for it.

[Update:] What have I tried?

I created an interface like this

interface Documents {
  data: Array | Object,
  id: Number
}

but this gives following error (red underline below array)

Generic type 'Array' requires 1 type argument(s).

If it makes any difference, I expect my array to be either empty or contain list of objects

Answer 1

You need to specify the underlying type of array, as Array is a type constructor. I would err towards primitive types where possible. Also, if your data is either an object, an empty array, or a list of objects, I would keep simple and just define it as a (possibly empty) list of objects. So you might end up with something like this:

type DocData = [object]
interface DocumentInterface {
  data: DocData
  id: number
}

class Doc implements DocumentInterface {
    data: DocData
    id: number

    constructor (data: DocData, id: number) {
        this.data = data
        this.id = id
    }
}

Answer 2

You can make Documents become a generic interface, your data need to be an array or a object, what is type of data you store in the array?, or what is type of the object? The type can be something, like User , Store ...

Example:

interface Documents<T extends object> {
  data: Array<T> | T;
  id: number; // best practice: https://www.typescriptlang.org/docs/handbook/declaration-files/do-s-and-don-ts.html 
}

And you have another type like:

interface IUser {
  name: string,
  email: string,
}

Now you need to create a document with data is a IUser :

const doc: Documents<IUser> = {
  id: 1,
  data: {
    name: 'Tom',
    email: 'example@mail.com'
  }
}

or data will store many IUser :

const docs: Documents<IUser> = {
  id: 1,
  data: [{
    name: 'Tom',
    email: 'example@mail.com'
  }]
}

Answer 3

class Document {
    private data: [] | object;
    private id: string;
  constructor (data: [] | object, id:string) {
    this.data = data
    this.id = id
  }
}