How to Create Sentiment Analysis Application using Node.js ?

// Import packages below
const express = require("express");
const natural = require("natural");
const stopword = require("stopword");

// Port and Host
const port = 5500;
const host = "127.0.0.1";

// Initialise our app
let app = express();

// Include Routes

// Listen
app.listen(port,host,()=>{
    console.log("Server is running...");
});

// Include Routes

app.post("/feedback",(request,response)=>{
    const { feedback } = request.body;
});

// Include npm packages
const express = require("express");
const natural = require("natural");
const stopword = require("stopword");

// For conversion of contractions to standard lexicon
const wordDict = {
    "aren't": "are not",
    "can't": "cannot",
    "couldn't": "could not",
    "didn't": "did not",
    "doesn't": "does not",
    "don't": "do not",
    "hadn't": "had not",
    "hasn't": "has not",
    "haven't": "have not",
    "he'd": "he would",
    "he'll": "he will",
    "he's": "he is",
    "i'd": "I would",
    "i'd": "I had",
    "i'll": "I will",
    "i'm": "I am",
    "isn't": "is not",
    "it's": "it is",
    "it'll": "it will",
    "i've": "I have",
    "let's": "let us",
    "mightn't": "might not",
    "mustn't": "must not",
    "shan't": "shall not",
    "she'd": "she would",
    "she'll": "she will",
    "she's": "she is",
    "shouldn't": "should not",
    "that's": "that is",
    "there's": "there is",
    "they'd": "they would",
    "they'll": "they will",
    "they're": "they are",
    "they've": "they have",
    "we'd": "we would",
    "we're": "we are",
    "weren't": "were not",
    "we've": "we have",
    "what'll": "what will",
    "what're": "what are",
    "what's": "what is",
    "what've": "what have",
    "where's": "where is",
    "who'd": "who would",
    "who'll": "who will",
    "who're": "who are",
    "who's": "who is",
    "who've": "who have",
    "won't": "will not",
    "wouldn't": "would not",
    "you'd": "you would",
    "you'll": "you will",
    "you're": "you are",
    "you've": "you have",
    "'re": " are",
    "wasn't": "was not",
    "we'll": " will",
    "didn't": "did not"
}

const port = 5500;
const host = "127.0.0.1";

let app = express();

app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use("/",express.static(__dirname + "/public"));


// Contractions to standard lexicons Conversion
const convertToStandard = text => {
    const data = text.split(' ');
    data.forEach((word, index) => {
        Object.keys(wordDict).forEach(key => {
            if (key === word.toLowerCase()) {
                data[index] = wordDict[key]
            };
        });
    });

    return data.join(' ');
}

// LowerCase Conversion
const convertTolowerCase = text => {
    return text.toLowerCase();
}

// Pure Alphabets extraction
const removeNonAlpha = text => {

    // This specific Regex means that replace all
    //non alphabets with empty string.
    return text.replace(/[^a-zA-Z\s]+/g, '');
}

// Analysis Route
app.post("/feedback", (request, response) => {
    console.log(request.body);

    // NLP Logic
    // Convert all data to its standard form
    const lexData = convertToStandard(request.body.feedback);
    console.log("Lexed Data: ",lexData);

    // Convert all data to lowercase
    const lowerCaseData = convertTolowerCase(lexData);
    console.log("LowerCase Format: ",lowerCaseData);

    // Remove non alphabets and special characters
    const onlyAlpha = removeNonAlpha(lowerCaseData);
    console.log("OnlyAlpha: ",onlyAlpha);

    // Tokenization
    const tokenConstructor = new natural.WordTokenizer();
    const tokenizedData = tokenConstructor.tokenize(onlyAlpha);
    console.log("Tokenized Data: ",tokenizedData);

    // Remove Stopwords
    const filteredData = stopword.removeStopwords(tokenizedData);
    console.log("After removing stopwords: ",filteredData);

    // Stemming
    const Sentianalyzer =
    new natural.SentimentAnalyzer('English', natural.PorterStemmer, 'afinn');
    const analysis_score = Sentianalyzer.getSentiment(filteredData);
    console.log("Sentiment Score: ",analysis_score);


    response.status(200).json({
        message: "Data received",
        sentiment_score: analysis_score
    })
});

app.listen(port, host, () => {
    console.log('Server is running...');
});

// Grab all HTML Elements 

// All containers
const feedback = document.getElementById("feedbacktext");
const wholeContainer = document.querySelector(".feedback");
const resultContainer = document.querySelector(".results");

// All controls
const submit_button = document.getElementById("submit");
const closeButton = document.querySelector(".close");

// Results
const emoji = document.querySelector(".emoji");
const sentiment = document.querySelector(".sentiment");

// Add event listener to submit button, send feedback and 
// name to our node js server application 
submit_button.addEventListener("click",()=>{
    console.log("Feedback: ",feedback.value);

    // Send POST request to our server
    const options = {
        method : "POST",
        body : JSON.stringify({
            feedback : feedback.value
        }),
        headers : new Headers({
            'Content-Type' : "application/json"
        })
    }

    // Use fetch to request server
    fetch("/feedback",options)
        .then(res=>res.json())
        .then((response)=>{
            console.log(response.sentiment_score);

            const score = response.sentiment_score;

            // Separate responses according to sentiment_score
            if(score > 0){
                emoji.innerHTML = "<p>&#128516;</p>";
                sentiment.innerHTML = "<p>&#10133; Positive</p>";
            }else if(score === 0){
                emoji.innerHTML = "<p>&#128528;</p>";
                sentiment.innerHTML = "<p>Neutral</p>";
            }else{
                emoji.innerHTML = "<p>&#128545;</p>";
                sentiment.innerHTML = "<p>&#10134; Negative</p>";
            }

            // Result Box should appear 
            resultContainer.classList.add("active");
            wholeContainer.classList.add("active");

        })
        .catch(err=>console.error("Error: ",err));

    // Clear all inputs after operation
    feedback.value = "";
});

// Close Button

closeButton.addEventListener("click",()=>{
    wholeContainer.classList.remove("active");
    resultContainer.classList.remove("active");
})