JavaScript returns undefined - AWS Comprehend

Question

I'm trying to set up a function in which detects the language of the text sample (through AWS API) but I get in nodeJs I get undefined.

const fs = require('fs');
var AWS = require('aws-sdk');
AWS.config.update({ region: 'eu-west-1' });


function languageDetection(test) {

    const params = { TextList: [test] };
    var comprehend = new AWS.Comprehend();
    comprehend.batchDetectDominantLanguage(params, function (err, data) {
        if (err) console.log(err, err.stack);
        else {
            const { ResultList } = data;
            const languages = ResultList[0]["Languages"];
            const detectedLanguage = languages[0]
            const detectedLanguageText = detectedLanguage["LanguageCode"];
            return detectedLanguageText
        }
    });
}

let aTextExample = 'This is a sample text'
const language = languageDetection(aTextExample)
console.log(language)

Answer 1

You will have to wait until you get a response. You can use a Promise

Try this

function languageDetection(test) {
  return new Promise(function(resolve, reject){
    const params = { TextList: [test] };
    var comprehend = new AWS.Comprehend();
    comprehend.batchDetectDominantLanguage(params, function (err, data) {
        if (err) return reject(err, err.stack);
        else {
            const { ResultList } = data;
            const languages = ResultList[0]["Languages"];
            const detectedLanguage = languages[0]
            const detectedLanguageText = detectedLanguage["LanguageCode"];
            resolve(detectedLanguageText);
        }
    });
  })
}