Redux-saga doesn't wait for response from API

Question

I use redux-saga and I created a generator checkUsername which perform the API call. I though that const username will equal to response from API, but I've got undefined.

function* checkUsername(action) {
  try {
    const username = yield call(Api.checkUsername, action.username);
    yield put({type: actions.USERNAME_CHECK_SUCCEEDED, username});
  } catch (e) {
    yield put({type: actions.USERNAME_CHECK_FAILED, message: e.message});
  }
}

Although in my checkUsername function, which call API res is equal {"isExist": false}:

 checkUsername(username) {
    fetch(url, {
    'GET',
    headers: {
      'Accept': 'application/json',
      'Content-Type': 'application/json',
    }
  }).then(response => response.json())
      .then(res => res)
      .catch(error => console.error(error));
 },

Why my const username is not equal {"isExist": false}?

Answer 1

In your checkUsername function you need to return the call to fetch().