Javascript Code Grammar Sentence Fixer

Javascript Code/Function to Correctly Format Text by [1] Capitalizing First Letter of Each Sentence, [2] Find and Fix Contractions that Don't Have Apostrophes Where They Should be Such as doesnt => doesn't, cant => can't, etc

Javascript Code/Function to Correctly Format Text by [1] Capitalizing First Letter of Each Sentence, [2] Find and Fix Contractions that Don't Have Apostrophes Where They Should be Such as doesnt => doesn't, cant => can't, etc.

function sentences_fixer(str) { // contractions that don't have the apostrophes let arrerr = [ "arent", "cant", "didnt", "doesnt", "dont", "hasnt", "havent", " hes ", " i ", " id ", " i'd ", " Ill ", " im ", " i'm ", " its ", " Its ", " ive ", " Ive ", " lets ", "musnt", " shes ", "thats", "theres", "theyd", "werent", "weve", "whatll", "whats", "wheres", "wont", "wheres", "wouldve", "youre", "youve" ] // corrections to the above words with missing contraction apostrophes let arrcorr = [ "aren't", "can't", "didn't", "doesn't", "don't", "hasn't", "haven't", " he's ", " I ", " I'd ", " I'd ", " I'll ", " I'm ", " I'm ", " It's ", " It's ", " I've ", " I've ", " let's ", "musn't", " she's ", "that's", "there's", "they'd", "weren't", "we've", "what'll", "what's", "where's", "won't", "where's", "would've", "you're", "you've" ] let result = str; // find and replace words without apostrophes with the correction for(let i = 0; i < arrerr.length; i++){ str= str.split(arrerr[i]).join(arrcorr[i]); } // capitalize first letter of each sentence str = str.replace(/(?<=(?:^|[.?!])\W*)[a-z]/g, i => i.toUpperCase()); return str; }