How to use the @google-cloud/language.LanguageServiceClient function in @google-cloud/language

// Imports the Google Cloud client library
const language = require('@google-cloud/language');

// Instantiates a client
const client = new language.LanguageServiceClient();

// The text to analyze
const text = 'Google Natural Language API is fantastic. It gives me great results and I love it.';

const document = {
  content: text,
  type: 'PLAIN_TEXT',
};

// Detects the sentiment of the text
client
  .analyzeSentiment({document: document})
  .then(results => {
    const sentiment = results[0].documentSentiment;

    console.log(`Text: ${text}`);

async function analyzeSyntaxOfText(text) {
  // [START language_syntax_text]
  // Imports the Google Cloud client library
  const language = require('@google-cloud/language');

  // Creates a client
  const client = new language.LanguageServiceClient();

  /**
   * TODO(developer): Uncomment the following line to run this code.
   */
  // const text = 'Your text to analyze, e.g. Hello, world!';

  // Prepares a document, representing the provided text
  const document = {
    content: text,
    type: 'PLAIN_TEXT',
  };

  // Detects syntax in the document
  const [syntax] = await client.analyzeSyntax({document});

  console.log('Tokens:');

'use strict';

const functions = require('firebase-functions');
const admin = require('firebase-admin');

// Follow instructions to set up admin credentials:
// https://firebase.google.com/docs/functions/local-emulator#set_up_admin_credentials_optional
admin.initializeApp({
  credential: admin.credential.applicationDefault(),
  // TODO: ADD YOUR DATABASE URL
  databaseURL: undefined
});

const language = require('@google-cloud/language');
const client = new language.LanguageServiceClient();
const express = require('express');
const app = express();


// Express middleware that validates Firebase ID Tokens passed in the Authorization HTTP header.
// The Firebase ID token needs to be passed as a Bearer token in the Authorization HTTP header like this:
// `Authorization: Bearer `.
// when decoded successfully, the ID Token content will be added as `req.user`.
const authenticate = async (req, res, next) => {
  if (!req.headers.authorization || !req.headers.authorization.startsWith('Bearer ')) {
    res.status(403).send('Unauthorized');
    return;
  }
  const idToken = req.headers.authorization.split('Bearer ')[1];
  try {
    const decodedIdToken = await admin.auth().verifyIdToken(idToken);

// TODO: Load the Natural Language ML API module
const Language = require('@google-cloud/language');

// END TODO

// TODO: Create a client object against the Language API
// using the Language.LanguageServiceClient function
// The LanguageServiceClient function accepts an options 
// object which is used to specify which project should be 
// billed for use of the API via the projectId property. 
// The projectId is retrieved from the config module. 
// This module retrieves the project ID from the 
// GCLOUD_PROJECT environment variable.

const language = new Language.LanguageServiceClient({
    projectId: config.get('GCLOUD_PROJECT')
});

// END TODO

function analyze(text) {
    // TODO: Create an object named document with the 
    // correct structure for the Natural Language ML API
    // TODO: Initialize object content & type properties
    // TODO: Set content from text arg
    // TODO: Set type to PLAIN_TEXT
    const document = {
        content: text,
        type: 'PLAIN_TEXT'
    };

const path = __dirname;

if (process.env.NODE_ENV === 'production') {
  const creds = process.env.GOOGLE_KEY
  const JSONcreds = JSON.parse(creds)
  process.env.GOOGLE_APPLICATION_CREDENTIALS = JSONcreds
} else {
  process.env.GOOGLE_APPLICATION_CREDENTIALS = `${path}/../../config/google_key.json`;
}

// Imports the Google Cloud client library
const language = require('@google-cloud/language');

// Instantiates a client
const client = new language.LanguageServiceClient();

const Fup = require('../../models/Fup');
const Word = require('../../models/Word');
const Like = require('../../models/Like');
const validateFupInput = require('../../validation/fups');

const getWordsFromFup = (fup, req) => {
  const document = {
    content: req.body.text,
    type: 'PLAIN_TEXT',
  };
  client
    .analyzeEntitySentiment({ document })
    .then((results) => {
      const entities = results[0].entities;

async function classifyTextInFile(bucketName, fileName) {
  // [START language_classify_gcs]
  // Imports the Google Cloud client library.
  const language = require('@google-cloud/language');

  // Creates a client.
  const client = new language.LanguageServiceClient();

  /**
   * TODO(developer): Uncomment the following lines to run this code
   */
  // const bucketName = 'Your bucket name, e.g. my-bucket';
  // const fileName = 'Your file name, e.g. my-file.txt';

  // Prepares a document, representing a text file in Cloud Storage
  const document = {
    gcsContentUri: `gs://${bucketName}/${fileName}`,
    type: 'PLAIN_TEXT',
  };

  // Classifies text in the document
  const [classification] = await client.classifyText({document});

// The sentiment field contains magnitude and score.
            node.send(msg);
        } // Input


        /**
         * Cleanup this node.
         */
        function Close() {
        } // Close


        // We must have EITHER credentials or a keyFilename.  If neither are supplied, that
        // is an error.  If both are supplied, then credentials will be used.
        if (credentials) {
            languageServiceClient = new language.LanguageServiceClient({
                "credentials": credentials
            });
        } else if (keyFilename) {
            languageServiceClient = new language.LanguageServiceClient({
                "keyFilename": keyFilename
            });
        } else {
            languageServiceClient = new language.LanguageServiceClient({});
        }

        node.on("input", Input);
        node.on("close", Close);
    } // SentimentNode

async function analyzeEntitySentimentOfText(text) {
  // [START language_entity_sentiment_text]
  // Imports the Google Cloud client library
  const language = require('@google-cloud/language');

  // Creates a client
  const client = new language.LanguageServiceClient();

  /**
   * TODO(developer): Uncomment the following line to run this code.
   */
  // const text = 'Your text to analyze, e.g. Hello, world!';

  // Prepares a document, representing the provided text
  const document = {
    content: text,
    type: 'PLAIN_TEXT',
  };

  // Detects sentiment of entities in the document
  const [result] = await client.analyzeEntitySentiment({document});
  const entities = result.entities;

async function analyzeSentimentOfText(text) {
  // [START language_sentiment_text]
  // Imports the Google Cloud client library
  const language = require('@google-cloud/language');

  // Creates a client
  const client = new language.LanguageServiceClient();

  /**
   * TODO(developer): Uncomment the following line to run this code.
   */
  // const text = 'Your text to analyze, e.g. Hello, world!';

  // Prepares a document, representing the provided text
  const document = {
    content: text,
    type: 'PLAIN_TEXT',
  };

  // Detects the sentiment of the document
  const [result] = await client.analyzeSentiment({document});

  const sentiment = result.documentSentiment;

function main() {
  const languageServiceClient = new language.LanguageServiceClient();
}