AWS Lambda Node.js to get change of status in EC2 instances.

index.js

const Slack = require("slack-node");
// Load the AWS SDK for Node.js
const AWS = require("aws-sdk");
// Set the region 
AWS.config.update({region: process.env.REGION});

// Create EC2 service object
var ec2 = new AWS.EC2();

function capitalizeFirstLetter(string) {
    return string.charAt(0).toUpperCase() + string.slice(1);
}

function checkDNS(dns) {
    if (dns != "") return dns;
    return "Not available until restart"
}

function composeMsg(infos) {

    var payload = {
        channel: process.env.SLACK_CHANNEL,
        username: process.env.SLACK_BOT_NAME,
        text: "EC2 Instances status in "+process.env.REGION,
        attachments: [{
            color: "#36a64f",
            text: "Details",
            fields: [],
            image_url: "🏢",
            thumb_url: "🏢"
        }]
    };
        
    infos.forEach(function(info, index) {
        payload['attachments'][0]['fields'].push({
            "title": "💻  "+capitalizeFirstLetter(info['name'])+" is "+info["status"],
            "value": "ID: "+info['id']+"; Public DNS: "+checkDNS(info["dns"])+";",
            "short": true
        });
    });

    return payload;

}

function slackNotifier(infos) {

    var payload = composeMsg(infos);

    var webhookUri = process.env.SLACK_WEBHOOK;

    var slack = new Slack();
    slack.setWebhook(webhookUri);

    slack.webhook(payload, function(err, response) {
        if (err) {
            console.log(err);
        }
    });

    return payload;

}

exports.handler = (event, context, callback) => {

    var params = {};

    ec2.describeInstances(params, function(err, data) {

        if (err) {
            console.log(err, err.stack);
        }
        else {
            var count = 0;
            var infos = [];
            
            data = JSON.parse(JSON.stringify(data));
            
            // for each instance
            for (var reservartion of data["Reservations"]) {
                
                var instance = reservartion["Instances"][0];
                infos.push({});

                // find id
                infos[count]["id"] = instance["InstanceId"];

                // find name
                for (var tag of instance["Tags"]) {
                    if (tag["Key"] == "Name") {
                        infos[count]["name"] = tag["Value"];
                        break;
                    }
                }

                // save status
                infos[count]["status"] = instance["State"]["Name"];

                // save dns and ip
                infos[count]["dns"] = instance["PublicDnsName"];
                infos[count]["ip"] = instance["PublicIpAddress"];
                
                count = count + 1;

            }

            console.log(infos);

            // send message
            var msg = slackNotifier(infos);
            callback(null, msg);
        }
    });
};