prettify.js

function prettify(document){
    // Turns an array of words into lowercase and removes stopwords
    const stopwords = stopwords_array
    // turn document into lowercase words, remove all stopwords
    var document = document.replace(/[.,]/g, '');
    let document_in_lowercase = document.split(" ").map(function(x){ return x.toLowerCase() });
    return document_in_lowercase.filter( x => !stopwords.includes(x) );
}