问通过JavaScript检测404资源

EN

function UrlExists(url) {
        var http = new XMLHttpRequest();
        http.open('HEAD', url, false);
        http.send();
        if (http.status == 404) {
             //  do something
        }
    }

var styleSheetExists = function(name) {
    for (var i in document.styleSheets) {
        if (typeof document.styleSheets[i] == "object") {
           link = document.styleSheets[i].href;
           if (link === null) {
               continue;
           }

           if (link.indexOf(name, link.length - name.length) !== -1) {
               return true;
           }
       }
   }
   return false;
}

$(document).ready(function() {
    console.log(styleSheetExists('jquery-ui.css'));
    console.log(styleSheetExists('doesnotexist.css'));
});