Missing region in AWS rekognition in node js - node.js

Question

//Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//PDX-License-Identifier: MIT-0 (For details, see https://github.com/awsdocs/amazon-rekognition-developer-guide/blob/master/LICENSE-SAMPLECODE.)
const AWS = require('aws-sdk')
const bucket = 'bucket' // the bucketname without s3://
const photo_source = 'source.jpg'
const photo_target = 'target.jpg'
const config = new AWS.Config({
accessKeyId: process.env.AWS_ACCESS_KEY_ID,
secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
region: process.env.AWS_REGION
})
const client = new AWS.Rekognition();
const params = {
SourceImage: {
S3Object: {
Bucket: bucket,
Name: photo_source
},
},
TargetImage: {
S3Object: {
Bucket: bucket,
Name: photo_target
},
},
SimilarityThreshold: 70
}
client.compareFaces(params, function(err, response) {
if (err) {
console.log(err, err.stack); // an error occurred
} else {
response.FaceMatches.forEach(data => {
let position = data.Face.BoundingBox
let similarity = data.Similarity
console.log(`The face at: ${position.Left}, ${position.Top} matches with ${similarity} % confidence`)
}) // for response.faceDetails
} // if
});
Above code is from official aws webpage (https://docs.aws.amazon.com/rekognition/latest/dg/faces-comparefaces.html). The code is for implementing comparing faces in image using node js. When comparing images using the above code a error occurs which says missing region on config. Then when i checked the code eventhough config object is created in this code but it is not being used anywhere. Can someone tell me where i must use the config object. If the error is appearing due to any other reason please tell me the reason