res_levis_frontend/test.js

var url = 'https://192.168.1.3:10002/realms/API.Server.local/protocol/openid-connect/token';
var params = 'grant_type=client_credentials&client_id=Fastapi&client_secret=wojuoB7Z5xhlPFrF2lIxJSSdVHCApEgC';
    
    
  // METHOD 1 (fetch POST)
    
let args = {
    "url": "https://192.168.1.3:10002/realms/API.Server.local/protocol/openid-connect/token",
    "options": {
        "method": "POST",
        "headers": {
            "Content-Type": "application/x-www-form-urlencoded"
        },
        "body": params
    }
};
if (args.options.body && typeof args.options.body !== 'string') args.options.body = JSON.stringify(args.options.body); fetch(args.url, args.options).then(response => response.json()).then(data => {console.log('fetchJson success'); console.log(data);}).catch((err) => {console.log('fetchJson error');console.log(err);})