JSFiddle - React, Tailwind, and code Playground

HTML

<form name="myForm" method="POST">
    <input type="text" name="isbn" />
    <button>Submit</button>
</form>
<p id="ouput"></p>

JavaScript

var form = document.forms.myForm,
    el = form.elements;

var isbnValidator = function(isbn) {
    return isbn.replace(/[^\dx]/ig, '').split('').map(function(el) {
        return /x/i.test(el) ? 10 : parseInt(el);
    }).reduce(function(prev, cur, idx, arr) {
        return prev * (idx === 1 ? arr.length : 1) + (arr.length - idx) * cur;
    }) % 11 === 0;
}

form.onsubmit = function() {
    alert(isbnValidator(el.isbn.value));
    return false;
}