# Refresh Token In Apollo Client

If your GraphQL api needs token refresh option, you can pass custom fetch function for Apollo Client.

    export const createApolloClient = (  url: string,  logout: () => void,  getAuthorizationData: () => { authorization: string },  refreshToken: () => Promise<    { accessToken: string; refreshToken: string } | undefined  >,) =>  new ApolloClientBase({    // ...other options    link: ApolloLink.from([      // ...other options      setContext(async (_, { headers }) => {        return {          headers: {            ...headers,            ...getAuthorizationData(),          },        };      }),      new HttpLink({        uri: url,        fetch: fetchWithTokenRefresh(logout, refreshToken),      }),    ]),  });

Custom fetch function for this request. You should tune `hasUnauthorizedError` and `isRefreshRequestOptions` to match your api.

    /** Global singleton for refreshing promise */let refreshingPromise: Promise<string> | null = null;/** Checks if GraphQl errors has unauthenticated error */const hasUnauthorizedError = (errors: Array<{ code?: ErrorCode }>): =>  Array.isArray(errors) &&  errors.some=> {    return error.status === 401; // Distinguish unauthorized error here  });/** Detects if customFetch is sending refresh request */const isRefreshRequestOptions = (options: RequestInit) => {  try {    const body = string);    return body.operationName === 'RefreshToken';  } catch (e) {    return false;  }};/** fetchWithTokenRefresh is a custom fetch function with token refresh for apollo */export const fetchWithTokenRefresh =  (    logout: () => void,    refreshToken: () =>       { accessToken: string; refreshToken: string } | undefined    >,  ) =>  async (uri: string, options: RequestInit): Promise<Response> => {    // already refreshing token, wait for it and then use refreshed token    // or use empty authorization if refreshing failed    if (      !isRefreshRequestOptions(options) &&      refreshingPromise &&      (options.headers as Record<string, string>)?.authorization    ) {      const newAccessToken = await refreshingPromise        .catch(() => {          // refreshing token from other request failed, retry without authorization          return '';        });            options.headers = {        ...(options.headers || {}),        authorization: newAccessToken,      };    }    return fetch(uri, options).then(async      const text = await response.text();      const json =      // check for unauthorized errors, if not present, just return result      if (        isRefreshRequestOptions(options) ||        !json?.errors ||                !hasUnauthorizedError(json.errors)      ) {        return {          ...response,          ok: true,          json: async () =>            new Promise<unknown>(resolve => {              resolve(json);            }),          text: async () =>            new Promise<string>(resolve => {              resolve(text);            }),        };      }      // If unauthorized, refresh token and try again      if (!refreshingPromise) {        refreshingPromise = refreshToken()          .then(async (tokens): Promise<string> => {            refreshingPromise = null;            if (!tokens?.accessToken) {              throw new Error('Session expired');            }            return tokens?.accessToken;          })          .catch(() => {            refreshingPromise = null;            // can't refresh token. logging out            logout();            throw new Error('Session expired');          });      }      // success or any non-auth error      return refreshingPromise        .then(async (newAccessToken: string) => {          // wait for other request's refreshing query to finish, when retry          return fetch(uri, {            ...options,            headers: {              ...(options.headers || {}),              authorization: newAccessToken,            },          });        })        .catch(async () => {          // refreshing token from other request failed, retry without authorization          return fetch(uri, {            ...options,            headers: {              ...(options.headers || {}),              authorization: '',            },          });        });    });  };