In my React Native 0.66 app, here is the fetch used to update backend db:

let update = {
  status:"BidPlaced",
  buyer_id:Null, //<<==how to pass NULL for update?
  buy_date:NULL,  //<<==how to pass NULL for update?
};


res = await fetch(url, {. 
  method: "POST",
  headers: {
    'Accept': 'application/json, text/plain',
    'Content-Type': 'application/json',   
  },
  body: JSON.stringify(update), 
});

there is a need to pass NULL value in fetch to back end (nodejs + sequelize/postgres) for update. I notice if empty string is used buyer_id: , buy_date: , then JSON.stringify will omit them since there is no value provided for both buyer_id and buy_date. What is the right way to send NULL in fetch to update back end which is nodejs and sequelize/postgres?