Send POST request in Google Apps Script with Headers and Body - google-apps-script

Question

I am trying to send a POST request in order to receive an Access Token in return.
The documentation is as follows:
Client Credentials
This is your first route to obtain an access_token to communicate with the API.
Route : POST https://api.helloasso.com/oauth2/token
Headers
Content-Type = application/x-www-form-urlencoded
Body
client_id = Your Client Id
client_secret = Your Client Secret
grant_type = client_credentials
Solution I tried
Based on this post, I tried the following code:
function qwe()
{
const url = 'https://api.helloasso.com/oauth2/token';
const headers = {
"client_id": "Your Client Id",
"client_secret": "Your Client Secret",
"grant_type": "client_credentials"
};
const options = {
'method' : 'post',
'contentType': 'application/x-www-form-urlencoded',
'headers': headers
};
const response = UrlFetchApp.fetch(url, options);
var data = JSON.parse(response);
Logger.log(data);
}
Upon running this, I get an error "Exception: Request failed for https://api.helloasso.com returned code 400. Truncated server response: {"error":"unauthorized_client","error_description":"client_id is not set"}".
I am a beginner, and would appreciate any help on this! Thank you in advance

Answer 1

Modification points:
In the case of UrlFetchApp, the default content type is application/x-www-form-urlencoded.
From your question and situation, I guessed that your Body might be required to be sent as form data.
If those points are reflected in your script, it becomes as follows.
Modified script:
function qwe() {
const url = 'https://api.helloasso.com/oauth2/token';
const data = {
"client_id": "Your Client Id",
"client_secret": "Your Client Secret",
"grant_type": "client_credentials"
};
const options = {
'method': 'post',
'payload': data
};
const response = UrlFetchApp.fetch(url, options);
console.log(response.getContentText())
}
Note:
If you tested this modified script, when an error occurs, please show the detailed error message and provide the official document. By this, I would like to confirm it.
Reference:
fetch(url, params)

Answer 2

Need to make it stringify first
'payload' : JSON.stringify(data)