Coverting array to indexed object in typescript

Question

I have an array of the following type.

interface IArray {
   id: "message1" | "message2" | "message3";
   message: string;
}

const myArray: IArray[] = [
   {
      id: "message1",
      message: "Here is your message 1"
   },
   {
      id: "message2",
      message: "Here is your message 2"
   }
]

I would like to convert it to an indexed object with types as following.

const myObject = {
   message1: "Here is your message 1",
   message2: "Here is your message 2"
}

I could write a function that converts the array into an object.

const myObject: any = {};
myArray.forEach((arrElement) => {
   myObject[arrElement.id] = arrElement.message;
});

But the myObject is of type any. while I want the myObject to have type with indexed keys depending on array id type.

What you mean by "But the objects keys do not get indexed with"? — palaѕн
– palaѕн, Commented May 3, 2020 at 14:56
An indexed object - in typescript defined object types have indexes. — Tanmoy Basak
– Tanmoy Basak, Commented May 3, 2020 at 15:26

Yosef Tukachinsky · Accepted Answer · 2020-05-03 15:00:26Z

2

const myArray = [{key: "message1",message: "Here is your message 1"},{key: "message2",message: "Here is your message 2"}]
const result = myArray.reduce((a,b)=>{
  a[b.key]=b.message;
  return a
}, {});
console.log(result);

answered May 3, 2020 at 15:00

Yosef Tukachinsky

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1 Comment

Tanmoy Basak Over a year ago

Please I need a typescript solution. This is not typescript. Note: I need definitions

Alessio Cantarella · Accepted Answer · 2020-05-03 20:05:10Z

1

You could use the forEach method:

JavaScript:

let myArray = [{
    id: "message1",
    message: "Here is your message 1"
  },
  {
    id: "message2",
    message: "Here is your message 2"
  }
];
let myObject = {};
myArray.forEach(item => {
  myObject[item.id] = item.message;
});
console.log(myObject);

TypeScript:

interface IArray {
  id: "message1" | "message2" | "message3";
  message: string;
}
const myArray: IArray[] = [{
    id: "message1",
    message: "Here is your message 1"
  },
  {
    id: "message2",
    message: "Here is your message 2"
  }
];
let myObject: any = {};
myArray.forEach(item => {
  myObject[item.id] = item.message;
});
console.log(myObject);

edited May 3, 2020 at 20:05

answered May 3, 2020 at 14:53

Alessio Cantarella

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3 Comments

Tanmoy Basak Over a year ago

Please I need a typescript solution. This is not typescript. Note: I need definitions

Alessio Cantarella Over a year ago

@TanmoyBasak I have updated my answer with a TypeScript syntax.

Tanmoy Basak Over a year ago

Thank you for the code. However, the resulting myObject has a type of any. While I am looking for a type: interface IObject { message1: string; message2: string; }

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