TypeError: Failed to execute 'fetch' on 'Window': Illegal invocation

export const sendSuggestion = ((data: any): Promise<any> => {
  console.log(JSON.stringify(data));
const apiUrl = `/api/suggest/`;
return fetch(apiUrl, {
    method: 'POST',
    headers: {'Content-Type': 'application/json'},
    body: JSON.stringify(data)
}).then(checkStatus)
    .then(r => r.json())
    .then(data => {
        console.log(data);
    });
});

const checkStatus = ((response: any) => {
  if (response.ok) {
    return response;
  } else {
    var error = new Error(response.statusText);
    console.log(error);
  //return Promise.reject(error);
  }
})

The script crashed with error TypeError: Failed to execute ‘fetch’ on ‘Window’: Illegal invocation After webkack it is looks:

exports.sendSuggestion = function (data) {
    var apiUrl = "/api/suggest/";
    return unfetch_1.default(apiUrl, {             //Code crashed here
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(data)
    }).then(checkStatus).then(function (r) {
        return r.json();
    }).then(function (data) {
        console.log(data);
    });
};
var checkStatus = function checkStatus(response) {
    if (response.ok) {
        return response;
    } else {
        var error = new Error(response.statusText);
        console.log(error);
    }
};