How to Refresh Token Using Google OAuth2 (Javascript/REST) - oauth-2.0

Question

I'm trying to get a new token from Google OAuth2 but I keep getting this error:
Here is my code (I'm using Expo to build React Native apps):
const uri = 'https://oauth2.googleapis.com/token'
const headerr = {
'Content-Type': 'Content-Type: application/x-www-form-urlencoded'
}
const bodyy = {
"client_id": '******************',
"refresh_token": `${refreshToken}`,
"grant_type":"refresh_token",
"access_type":"offline"
}
const fitnesss = await fetch(uri, {
method: "POST",
headers: headerr,
body: JSON.stringify(bodyy)
});
fitnesss.json().then(res => {
console.log(res)
})
Does anyone know how to solve this?

Answer 1

unsupported grant type means that the grant type refresh token is not supported with the language you are using.
The reason for this is that JavaScript is client sided which would mean that you would need to have the refresh token in the code. Anyone who viewed the source in the browser would be able to see and use your refresh token.
To use refresh tokens use a server sided language. For example Node.js
const fs = require('fs');
const readline = require('readline');
const {google} = require('googleapis');
// If modifying these scopes, delete token.json.
const SCOPES = ['https://www.googleapis.com/auth/drive.metadata.readonly'];
// The file token.json stores the user's access and refresh tokens, and is
// created automatically when the authorization flow completes for the first
// time.
const TOKEN_PATH = 'token.json';
// Load client secrets from a local file.
fs.readFile('credentials.json', (err, content) => {
if (err) return console.log('Error loading client secret file:', err);
// Authorize a client with credentials, then call the Google Drive API.
authorize(JSON.parse(content), listFiles);
});
/**
* Create an OAuth2 client with the given credentials, and then execute the
* given callback function.
* #param {Object} credentials The authorization client credentials.
* #param {function} callback The callback to call with the authorized client.
*/
function authorize(credentials, callback) {
const {client_secret, client_id, redirect_uris} = credentials.installed;
const oAuth2Client = new google.auth.OAuth2(
client_id, client_secret, redirect_uris[0]);
// Check if we have previously stored a token.
fs.readFile(TOKEN_PATH, (err, token) => {
if (err) return getAccessToken(oAuth2Client, callback);
oAuth2Client.setCredentials(JSON.parse(token));
callback(oAuth2Client);
});
}
/**
* Get and store new token after prompting for user authorization, and then
* execute the given callback with the authorized OAuth2 client.
* #param {google.auth.OAuth2} oAuth2Client The OAuth2 client to get token for.
* #param {getEventsCallback} callback The callback for the authorized client.
*/
function getAccessToken(oAuth2Client, callback) {
const authUrl = oAuth2Client.generateAuthUrl({
access_type: 'offline',
scope: SCOPES,
});
console.log('Authorize this app by visiting this url:', authUrl);
const rl = readline.createInterface({
input: process.stdin,
output: process.stdout,
});
rl.question('Enter the code from that page here: ', (code) => {
rl.close();
oAuth2Client.getToken(code, (err, token) => {
if (err) return console.error('Error retrieving access token', err);
oAuth2Client.setCredentials(token);
// Store the token to disk for later program executions
fs.writeFile(TOKEN_PATH, JSON.stringify(token), (err) => {
if (err) return console.error(err);
console.log('Token stored to', TOKEN_PATH);
});
callback(oAuth2Client);
});
});
}