WooCommerce Name Your Price - disable input

nyp-disable-input.js

jQuery(document).ready(function($) {

  //get the price in the input
  var originalPrice = $('input#nyp').val()
  var newPrice = originalPrice;
  //need the product id so a cookie can be set against it, probably won't work if I change themes - but works with storefront
  var productId = parseInt($('main#main > div').attr('id').replace('product-', ''))
  //does a cookie exist for this product id?
  var cookie = getCookie('haggledon-' + productId)
  if (cookie != null) {//the cookie exists, therefore this person has 'haggled' within 24 hours. Disable the price input.
    $('input#nyp').prop('disabled', 'true')
  }
  $('input#nyp').on('blur', function() {//have they input a 'haggle' price?
    newPrice = $('input#nyp').val();
    if (newPrice != originalPrice) {//prices differ, they only get one chance, disable the input
      $('input#nyp').prop('disabled', 'true')
      if (null == cookie) {//write the cookie if it doesn't exist
        cookie = "haggledon-" + productId + "=true;path=/;max-age=86400";
        document.cookie = cookie
      }
    }
  })
})

function getCookie(name) {//reads cookies, returns the one named 'name' if exists, else returns null. Copy & paste from stackexchange or something so I didn't learn anything here :(
  var re = new RegExp(name + "=([^;]+)");
  var value = re.exec(document.cookie);
  return (value != null) ? unescape(value[1]) : null;
}