how do you declare an array of objects inside typescript?

Question

I would like to specify a function that takes an array of objects as a parameter, but I don't have a particular type defined for the object (a sort of "anonymous type")

bagTotal = (products) => {
 // function does stuff
}

I understand I can do this:

bagTotal = (products: any[]) => {
 // function does stuff
}

but this is a bit more relaxed then what I want: to be strict with typescript.

products is an array of the same-looking objects; all objects have a name, a price and a description.

how can I declare that?

I want to do something like

bagTotal = (products: [{name: string, price: number, description: string}]) => {
 // function does stuff
}

but that's not right. How can I declare this?

Answer 1

You're almost there, the placement of the brackets is just wrong:

{name: string, price: number, description: string}[]

The way you had it isn't entirely wrong, but it means something else: it means an array with exactly one item of this type.

---

I'd also recommend extracting it to an interface, it'd make the type reusable and the thing easier to read:

interface Product {
    name: string;
    price: number;
    description: string;
}

const products: Product[];

Answer 2

I think you must declare the class "Product" so you can declare a Product array like this:

products: Product[];

and pass it as a parameter like this:

bagTotal = (products: Product[]) => {
 // function does stuff
}

To have the class you can do a new.ts file with this code:

export class Product {
  name: String;
  price: Number;
  description: String;
}

I wish that helped!

Thank you.

Answer 3

The generic array type Array<elemType> provides a straightforward way to declare an array of objects:

bagTotal = (products: Array<{name: string, price: number}>) => {
   ...
}

Answer 4

If you are declaring an array of a specific object and want to specify type for variables in the objects, I would create a class for the object like this:

class Item(){
    name: string;
    description: string;
    etc: any

  constructor() {
    this.name;
    this.description;
    this.etc;
}}

Then you can specify the array as an array of item objects:

itemArray: Array<Item>;