convert JSON string to JAVASCRIPT Object in Typescript

Question

Hi every one I have two JSON string

[{desc:"john",number:"22",designation:"manager"}]

another JSON string

[{name:"creek",ID:"198",role:"developer"}]

so i need to map first JSON file with second JSON file

my output should be like this

[{desc:"creek",number:"198",designation:"developer"}]

so here i thought while converting our JSON string to JAVASCRIPT object only we need to replace the attributes..

can any one help me with this Thanks...

So, what did you try? Can you post your code on https://jsfiddle.net or something? — Dale Nguyen, Jun 17 '18 at 22:27
See [How can I merge properties of two JavaScript objects dynamically?](https://stackoverflow.com/questions/171251/how-can-i-merge-properties-of-two-javascript-objects-dynamically) — xmojmr, Jun 18 '18 at 07:04

score 0 · Answer 1 · answered Feb 28 '21 at 21:08

You have two distinct types, which we can define typescript types for.

type FormatOne = {
  desc: string;
  number: string;
  designation: string;
}

type FormatTwo = {
  name: string;
  ID: string;
  role: string;
}

We can create a function to map from one type to the other.

const twoToOne = ({name, ID, role}: FormatTwo): FormatOne => ({
  desc: name,
  number: ID,
  designation: role,
})

When parsing JSON from a string, you have to assert the type with as because typescript does not know what the type will be. We can say that it will be an array with a mix of both types.

const str = '[{desc:"john",number:"22",designation:"manager"}, {name:"creek",ID:"198",role:"developer"}]';
const arr = JSON.parse(str) as Array<FormatOne | FormatTwo>;

If you know that you have an array of all FormatTwo then reformatting it is as simple as calling array.map(twoToOne).

When you have a mixed array, we need to check each element and conditionally call the converter. We use 'name' in item as a type guard to see if the item is FormatTwo.

const fixed = arr.map( item => 
  ('name' in item) ? twoToOne(item) : item
);

This new array fixed has the type FormatOne[] with no assertions required.

convert JSON string to JAVASCRIPT Object in Typescript

1 Answers1