Check Broken Links in a Page JS/JQuery

file.js

// Copy & paste below code in browser console.
function urlExists(url, callback) {
  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4) {
      callback(xhr.status < 400);
    }
  };
  xhr.open('HEAD', url);
  xhr.send();
}

jQuery('a').each(function(e){
var el =  jQuery(this);
var someUrl = el.attr('href');
var url_exists = true;
urlExists(someUrl, function(exists) {
    console.log('"%s" exists?', someUrl, exists);
  if(exists == false){
   el.css('background', 'yellow');
  }
});

});