Type definition for array with objects in TypeScript

Question

How can be defined types in TypeScript for en such array:

export const AlternativeSpatialReferences: Array< ??? > = [
    {
        '25833': 25833
    },
    {
        '25832': 25832
    },
    {
        '25831': 25831
    },
    {
        'Google': 4326
    } 
];

Now I just use Array<{}>, but want define properly.

Solution 1

If you want to define an object which property names are not known at compile time and which values are numbers, you should use an "index signature" (Thanks @Joe Clay):

interface MyObject {
    [propName: string]: number;
}

Then you can write:

export const AlternativeSpatialReferences: MyObject[] = [
    {
        '25833': 25833
    },
    {
        '25832': 25832
    },
    {
        '25831': 25831
    },
    {
        'Google': 4326
    } 
];

Solution 2

in typescript you make use of any type ,

any used for - need to describe the type of variables that we do not know when we are writing an application.

 Array<any>

---

if you want to go for some strong type than you should create new class with two property

public class KeyValue
{
  key:string;
  value:number;
}

 let myarray: KeyValue[] = new Array<KeyValue>();
 myarray.push({key: '25833' , value : 25833});
 myarray.push({key: 'Google' , value : 123});

and convert your current array values in strong type.

Comments

[indexoutofbounds]

Why any, those are obviously objects. Array<object> would be more appropriate here, imho!

[Joe Clay]

In case people reading this answer want to find further info - this syntax is called an 'index signature'.

[klugjo]

@JoeClay Thanks, I didnt know that. updated my answer with the information