Code#

var co = require('co');
var mongoose = require('mongoose');

let conn = null;

const uri = 'mongodb://username:password@mongourl:port/databaseName';

exports.handler = function(event, context, callback) {
  const requestBody = JSON.parse(event.body);
  context.callbackWaitsForEmptyEventLoop = false;

  run(requestBody).
    then(res => {
      callback(null, res);
    }).
    catch(error => callback(error));
};

function run(requestBody) {
  return co(function*() {
    if (conn == null) {
      conn = yield mongoose.createConnection(uri, {
        bufferCommands: false,
        bufferMaxEntries: 0
      });
      conn.model('collectionName', new mongoose.Schema({
        schedule: String,
        occupancy: Number,
        count: Number,
        price: Number,
        time: String,
        link: String
      }));
    }

    const M = conn.model('Bookings');
    const doc = yield M.findOneAndUpdate({"collectionName": requestBody.schedule}, {$set:{count: requestBody.count}});
    console.log(doc)
    const response = {
      statusCode: 200,
      body: JSON.stringify(doc)
    };
    return response;
  });
}

If you want an in depth explanation of the code feel free to follow my example from yesterday where I explained how to get data from MongoDB with Netlify functions. The only difference in code is that your const doc variable will be making a request to find a specific entry and update using the findOneAndUpdate method. An example post request for your new lambda would be

          axios.post('/.netlify/functions/postSchedule', update).then(res => {
            this.setState({success: true});
          })

As you can see, nothing changes in how you would code your friend end to make a post request! Tomorrow I will show an example for another function, this time we will be integrating our lambda with Stripe to make payments without a backend.