It is common function to fetch or post data using fetch.

requestHelper.js

export const checkAuth = () => {
  let localAuth = localStorage.getItem('auth')
  if(localAuth){
    return JSON.parse(localAuth)
  }
  return false
}
export const requestHelper = (url, method, headers, data) => {
  let token = checkAuth()

  let requestLoad = {
    method,
    headers: {
      ...headers,
      Accept: "application/json",
      "Content-Type": "application/json"
    },
    body: JSON.stringify(data)
  };
  if(token){
    requestLoad = {
      method,
      headers: {
        ...headers,
        Accept: "application/json",
        "Content-Type": "application/json",
        "Authorization": `Bearer ${token.jwt ? token.jwt: '..'}`
      },
      body: JSON.stringify(data)
    };
  }
  let getLoad = {
    method,
    headers: { ...headers, "Content-Type": "application/json" }
  };
  if(token){
    getLoad = {
      method,
      headers: { ...headers, "Content-Type": "application/json", "Authorization": `Bearer ${token.jwt ? token.jwt: '..'}` }
    };
  }
  return  fetch(`${url}`, method === "GET" ? getLoad : requestLoad);
};