How can I rewrite the offset class of Kafka Node in Kafkajs's code?

Question

I want to switch the javascript kafka library from kafka node to kafkajs. I want to find a way to wrap the below code which is the offset module originally from kafka node. How can I rewrite the whole function and also the consumer.on("offsetOutOfRange") function?

Code:

const kafkaClient = new kafka.KafkaClient({kafkaHost: '127.0.0.1'});
const kafka_offset = new kafka.Offset(kafkaClient);
kafka_offset.fetch(
    [{ topic: "testTopic",  partition: 0, time: -1, maxNum: 1 }],
    function(err, kafka_data) {
        if (err) {
            console.log(err);
            return;
        }
        const latest_offset = kafka_data["testTopic"]['0'][0];

    consumer = new kafka.Consumer(
        kafkaClient,
        [{ topic: "testTopic", partition: 0, offset: latest_offset -1}],
        {
            groupId: 'testing',
            autoCommit: true,
            fromOffset: true,
        }
    );

    consumer.on('offsetOutOfRange', obj => {});
    consumer.on('error', err => {logger.error('error: ', err);});
    consumer.on('message', message => {});
});