Docusign - Axios CORS (Working on Postman) - vue.js

Question

I'm trying to make this API call from my vue.js SPA.
this.$apiCallDocusign.post('/oauth/token', {
grant_type: 'urn:ietf:params:oauth:grant-type:jwt-bearer',
assertion: '{myJWT}'
})
$apiCallDocusign is:
import axios from 'axios'
var h_ds = {}
h_ds = {
"Content-Type": "application/json"
}
const apiUrlDocusign = 'https://account-d.docusign.com'
const apiCallDocusign = axios.create({
baseURL: apiUrlDocusign,
headers: h_ds
})
export default apiCallDocusign
But i get CORS error:
Access to XMLHttpRequest at 'https://account-d.docusign.com/oauth/token' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: Redirect is not allowed for a preflight request.
It works in Postman or Terminal with curl... Thanks in advance

Answer 1

Several issues here:
The only OAuth flow that may be used from a SPA to DocuSign is the Implicit grant flow. It works fine from a SPA (I use it myself.) JWT grant can't be used since there is no way to protect the needed private key from others.
An alternative is to have a lightweight server app that generates a DocuSign Access Token by using the JWT grant and then returns it to your SPA. Be careful to secure the server app against bad guys.
You will also need to create a private CORS gateway for use by your application since DocuSign doesn't yet support CORS. Docs for creating a private CORS gateway.
To help raise the profile of CORS, please ask your DocuSign contacts
to add your name/organization to internal ticket PORTFOLIO-1100.
CORS is on our roadmap but is not yet scheduled.