Discord OAuth2 - Exchange code to access token. Fixes Invalid Code error

main.js

let code = ...
let DISCORD_CLIENT_ID;
let DISCORD_CLIENT_SECRET;
let DISCORD_REDIRECT_URI;


let code_exchange = await fetch("https://discordapp.com/api/oauth2/token", {
    headers: {
        'Content-Type': 'application/x-www-form-urlencoded',
    },
    'method': 'POST',
    body: new URLSearchParams({
        client_id: DISCORD_CLIENT_ID,
        client_secret: DISCORD_CLIENT_SECRET,
        grant_type: 'authorization_code',
        redirect_uri: DISCORD_REDIRECT_URI,
        code: code,
    })
})  
// Thanks https://stackoverflow.com/a/58437909/
// Thanks https://msyyn.medium.com/how-to-add-discord-oauth-to-your-sveltekit-web-application-7c2e69d7656e

console.log(await code_exchange.json();)