This code works fine for me (using the PolkadotJS API):
import { ApiPromise, WsProvider } from "@polkadot/api";
export const fetchCollatorCandidates = async () => {
const provider = new WsProvider("wss://karura.api.onfinality.io/public-ws");
const api = new ApiPromise({ provider });
await api.isReadyOrError;
const candidates = await api.query.collatorSelection.candidates();
console.log(candidates.toHuman())
}
Output:
[
'ofbMGzDpuJttjypUk7SsV4n1omwSxA2gKYXSEDM3gMahNuN',
'op7G2ofug2Q2n1Bq3uUGzkNdSp68S93beMQkjjyDxnPREnk',
'qyf2KVDbBmF3MjRgmyFpQrNUnoxhp9AWCJrywysQcwXaiyb',
'raCf56Liw9dKJiqXSJMVoVV9eyV9s8DQoQD5r1TMcPoFM4B',
'rwGFKTBauckjEieq3xauaiDXxjfarZ198KXXVZupa9Dr6xm',
'sBwVWToF55CbuyBz3WEqDggniu8Gx18DkTQg4cagsCJsgVf',
'sgxpvRrL2VpAqhLPqC9up2u7gf1pCpR9c8vB7XdxnBpjxUC',
't4HMEqx3kW8ADAzKn5YWhAUQPdsZw7xFd39WLxRW193HYfh',
'tbjKCiq9k2p6L4xLJ9H7mAHs8FBE76aG4KcDapUbUnifjnr',
'tyBG83iCBH5zAx7zd3kvTzEJAGY8nuH2HsTtvf6YwCSwwVL'
]