Converting a typescript class object with dictionary to a JSON string

Question

I'm looking for a way to convert my typescript class with dictionary to a JSON object without the brackets.

this is my class

export class MediaTagRequest {
    tags: Map<string, string>; 
    constructor(tags: Map<string, string>) {
      this.tags = tags;
    }
}

My instantiation

   let tags = new Map<string, string>();
   tags.set("city", "Karachi");  

   let mediatagRequest = new MediaTagRequest(tags);
   const headers = { 'content-type': 'application/json'}   
   const body = JSON.stringify(Object.keys(mediatagRequest.tags.entries()));

My current output:

[["city","Karachi"]]

My desired output:

{
    "tags": {
        "city": "Karachi"
    }
}

Can someone help me please, thank you.

VLAZ · Accepted Answer · 2021-01-04 16:43:31Z

You can convert a map to an object directly by using Map#entries and Object.fromEntries.

Here is an example:

const m = new Map();

m.set("foo", "hello");
m.set("bar", "world");

const obj = Object.fromEntries(m.entries());

console.log(obj);

You can further leverage the replacer parameter of JSON.stringify to directly do this when converting an entire object:

function mapReplacer(key: string | number | Symbol, value: any) {
  if (value instanceof Map) {
    return Object.fromEntries(value.entries());
  }
  
  return value;
}

class MediaTagRequest {
    tags: Map<string, string>; 
    constructor(tags: Map<string, string>) {
      this.tags = tags;
    }
}

let tags = new Map<string, string>();
tags.set("city", "Karachi");  

let mediatagRequest = new MediaTagRequest(tags);

console.log(JSON.stringify(mediatagRequest, mapReplacer))

Playground Link

JavaScript demo:

function mapReplacer(key, value) {
  if (value instanceof Map) {
    return Object.fromEntries(value.entries());
  }
  
  return value;
}

class MediaTagRequest { 
    constructor(tags) {
      this.tags = tags;
    }
}

let tags = new Map();
tags.set("city", "Karachi");  

let mediatagRequest = new MediaTagRequest(tags);

console.log(JSON.stringify(mediatagRequest, mapReplacer))

Chandan · Accepted Answer · 2021-01-04 16:21:32Z

1

You can use any of this to create object and then create response body using it

Option 1

let jsonObject = {};
tags.forEach((value, key) => {  
    jsonObject[key] = value;
});

Option 2

let jsonObject = {};
for (let entry of tags.entries()) {
    jsonObject[entry[0]] = entry[1];
}

Option 3

let jsonObject = {};
for (let key of tags.keys()) {  
    jsonObject[key] = value;          
}

creating response body

const body = JSON.stringify({
    tags: jsonObject
});

edited Jan 4, 2021 at 16:21

answered Jan 4, 2021 at 16:14

Chandan

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1 Comment

Kyuzo Over a year ago

ah yes I already added the last line that you added to your solution. Thanks :)

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