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.

klugjo · Accepted Answer · 2017-12-16 05:06:42Z

8

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
    } 
];

edited Dec 16, 2017 at 5:06

answered Dec 15, 2017 at 9:50

klugjo

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2 Comments

Joe Clay Over a year ago

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

klugjo Over a year ago

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

Pranay Rana · Accepted Answer · 2017-12-15 09:45:58Z

5

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.

edited Dec 15, 2017 at 9:45

answered Dec 15, 2017 at 9:39

Pranay Rana

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2 Comments

indexoutofbounds Over a year ago

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

Timo Over a year ago

I needed Array<any> as stated in the answer as opposed to @indexoutofbounds comment because object resulted in foo does not exist on {}

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