Nodejs Serverless code for https://github.com/RealDyllon/react-supermarket-tracker

giant-delivery.js

const https = require('https');
const querystring = require('querystring');

exports.handler = async(event) => {
    let dataString = '';

    const httpOrigin = event.headers.origin

    const allowedOrigins = [
        "https://supermarkets.dyllon.dev"
    ]

    const isAllowed = allowedOrigins.indexOf(httpOrigin) > -1

    // grab our params from the lambda proxy integration
    const reqParamsData = {
        postal_code: (event &&
                event.queryStringParameters) ?
            event.queryStringParameters.postcode : "000000"
    }

    // console.log("postcode", reqParamsData.postal_code)

    const reqParams = querystring.stringify(reqParamsData);

    const reqOptions = {
        hostname: 'giant.sg',
        path: '/checkout/cart/checkdelivery?' + reqParams,
        headers: {

        }
    }

    const response = await new Promise((resolve, reject) => {

        // define the https request
        https.get(reqOptions, res => {
                //append to data string in real time
                res.on('data', chunk => {
                    // console.log("chunk", chunk)
                    dataString += chunk;
                });
                //when we've got all the data:
                res.on('end', () => {

                    // console.log("dataString", (dataString))

                    let dataObj = JSON.parse(dataString)
                    
                    console.log(
                            {
                                postcode: reqParamsData.postal_code,
                                httpOrigin: httpOrigin
                            }
                        )

                    let outputString = JSON.stringify({
                        ...dataObj,
                        apiEcho: {
                            postcode: reqParamsData.postal_code === "000000" ?
                                "missing!!!" : reqParamsData.postal_code,
                            httpOrigin: httpOrigin
                        },
                        event

                    })

                    resolve({
                        statusCode: 200,
                        headers: {
                            "Access-Control-Allow-Origin":
                                isAllowed ?
                                 httpOrigin
                            : "https://supermarkets.dyllon.dev",
                            "Access-Control-Allow-Headers": "Content-Type",
                            "Access-Control-Allow-Methods": "OPTIONS,POST,GET"
                        },
                        body: outputString
                    });
                });
            })
            // abort in case of error
            .on('error', (e) => {
                reject({
                    statusCode: 500,
                    headers: {
                        "Access-Control-Allow-Origin": isAllowed ?
                            httpOrigin : "https://supermarkets.dyllon.dev",
                        "Access-Control-Allow-Headers": "Content-Type",
                        "Access-Control-Allow-Methods": "OPTIONS,POST,GET"
                    },
                    body: 'Something went wrong!'
                });
            });

    });

    return response;
};