oapi.js

// Obvious API - REDUX 
// https://hackernoon.com/o-api-an-alternative-to-rest-apis-e9a2ed53b93c

const ACTIONS = {
  USERS: {
    CART: {
      ADD: 'ADD_PRODUCT_TO_CART',
    },
    SIGN_IN: 'SIGN_IN',
    SIGN_OUT: 'SIGN_OUT',
  },
  PRODUCTS: {
    GET_PRODUCT: 'GET_PRODUCT',
    GET_PRODUCTS: 'GET_PRODUCTS',
    ADD_PRODUCT_TO_CART: 'ADD_PRODUCT_TO_CART',
  },
};

const handlers = {
  [ACTIONS.PRODUCTS.ADD_PRODUCT_TO_CART]: require('./handlers/addProductToCart.js'),
  [ACTIONS.PRODUCTS.GET_PRODUCT]: require('./handlers/getProduct.js'),
  [ACTIONS.PRODUCTS.GET_PRODUCTS]: require('./handlers/getProducts.js'),
  [ACTIONS.USERS.SIGN_IN]: require('./handlers/signIn.js'),
  [ACTIONS.USERS.SIGN_OUT]: require('./handlers/signOut.js'),
};


app.post('/api', (req, res) => {
  const handler = handlers[req.body.action];
  
  if (handler) {
    handler(req, res);
  } else {
    console.error(`${req.body.action} doesn't have a handler`);
    
    res.sendStatus(500); // or whatever you want to do
  }
});

function addProductToCart(data) {
  sendToServer('addProductToCart', data);
  // also update the UI and maybe client-side store
}

function sendToServer(action, data) {
  return fetch('/api', {
    method: 'POST',
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify({ action, data })
  });
}