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javascriptarraysreactjstypescripttypes
Shiva Sai
Shiva Sai

Reputation: 463

typescript defining array with named objects

I am struggling to define a type for the array with named objects

below is the sample code.

now i have to define the type for the s in typescript

 let s =[12,3,4]
 s['data']={'x':0}
 console.log(s) // [12,3,4,data:{'x':0}]

now how to define the type for the s

can anyone please guide

Upvotes: 0

Views: 897

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1075239

It's probably best not to do this. But you can do it, by using an intersection type, in this case:

type AugmentedNumberArray = number[] & {
    data?: {x: number};
};

That's a type that's both a number array and an object with an optional data property that can be an object with an x property with a number value.

Playground Link

But as soon as you do something like s2 = s.map(v => v * 2), you'll lose the data property, because map (like all array methods) only deals with the array-like part of the object, not any other properties it may have.

Instead, though, I'd recommend defining an object that has both the named properties (data or whatever) and an array of numbers:

interface MyType {
    data?: {x: number};
    values: number[];
}

Then using it like this:

let s: MyType = {values: [12,3,4]};
s['data'] = {'x':0}; // Or idiomatically: s.data = ...
console.log(s);

Playground Link

Upvotes: 2

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