promisified.js

 const fetchShipengineDirectLoginUrl = (sellerId) => {
  return new Promise((res, rej) => {
    jsonFetch('/shipengine-direct-login', {
      method: 'POST',
      body: {
        sellerId: `se-${sellerId}`,
      },
    }).then((resp) => {
      console.log('DATA FROM EXPRESS SERVER: ', resp.body.redirect_url);
      res(resp.body.redirect_url);
    }).catch((err) => {
      console.log('ShipEngine Direct Login Error: ', err);
      rej(err);
    })
  )
};