Data of type 'new Map()' is not getting fetched in browser, but works fine in server side.

[yan5]

Describe the bug

If we return data of type new Map() from corresponding page endpoints, the component getting rendered in browser is unable to get the data, while server side is able to get it correctly.

Reproduction

index.svelte

<script>
	export let initialData;
	let map = initialData.map;
	console.log('in index.svelte map', map);
</script>

index.js

export async function get({ params }) {
    let map = new Map();
    map.set("key", "value");
    let initialData = { "map": map }
    return {
        body: {
            initialData
        }
    };
};

Below is what we see, as you can see on server side it shows map values {'key' : 'value'}, but on the browser its empty.
Moreoever, the data type itself is changed, on server its still Map, but on browser its changed to dictionary ({}).

But if we change the type to diction in index.js as follows

export async function get({ params }) {
    let map = {};
    map["key"] = "value";
    let initialData = { "map": map }

    return {
        body: {
            initialData
        }
    }
}

then both server and browser gets the data correctly as shown below.

Logs

No response

System Info

System:
    OS: Linux 5.15 Ubuntu 22.04 LTS 22.04 LTS (Jammy Jellyfish)
    CPU: (8) x64 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
    Memory: 3.03 GB / 15.42 GB
    Container: Yes
    Shell: 5.1.16 - /bin/bash
  Binaries:
    Node: 16.15.0 - ~/.nvm/versions/node/v16.15.0/bin/node
    npm: 8.13.2 - ~/.nvm/versions/node/v16.15.0/bin/npm
  Browsers:
    Brave Browser: 103.1.41.96
    Chrome: 103.0.5060.114
    Firefox: 102.0.1
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.55 
    @sveltejs/kit: next => 1.0.0-next.367 
    svelte: ^3.46.0 => 3.49.0 
    vite: ^2.9.13 => 2.9.14

Severity

serious, but I can work around it

Additional Information

No response

[gtm-nayan]

Duplicate #5358 #4944