check_running_instances.js

const AWS = require('aws-sdk');
AWS.config.region = 'us-west-2';

const ec2 = new AWS.EC2();

var webhook = '<Slack WebHook URL>';

exports.handler = function(event, context) {
    console.log('Start');

    var list = [];
    var params = {
        DryRun: false,
        MaxResults: 10,
        Filters: [{
            Name: 'instance-state-name',
            Values: ['running']
        }]
    };

    ec2.describeInstances(params, function(err, data) {
        if (err) {
            consle.log(err, err.stack);
        } else {
            for (i = 0; i < data.Reservations.length; i++) {
                instance_id = "> Instance ID: " + data.Reservations[i].Instances[0].InstanceId;

                list.push(instance_id);
            }

            if (list.length === 0) {
                context.succeed("No Running Instance.");
            } else {
                var text = "Please check the running instances in us-west-2 (Oregon)";
                var pray = ":pray: :pray: :pray:";
                text = text + "\\n" + list.join('\\n') + "\\n" + pray;

                var exec = require('child_process').exec;
                var cmd = 'curl -X POST --data-urlencode \'payload={"text": "' + text + '"}\' ' + webhook;

                exec(cmd, function(err, stdout, stderr) {
                    context.succeed(stdout);
                }); 
            }
        }
    });

    console.log('Finish');
};