html - Delete a cookie, javascript -

i'm trying conform italian cookie law banner notify cookies left website. used (and changed little bit) banner code made available google (https://www.cookiechoices.org/)

the banner works fine added little function (delete_cookie) in order let user delete manually cookie, left banner, clicking on link in cookie policy page. made tests , can't manage delete damn cookie when click on link :) (i'm working in local)

    (function(window) {    if (!!window.cookiechoices) {     return window.cookiechoices;   }    var document = window.document;   // ie8 not support textcontent, should fallback innertext.     var supportstextcontent;   try{     supportstextcontent = ('textcontent');   } catch(e){     supportstextcontent = false;   }    var cookiechoices = (function() {      var cookiename = 'displaycookieconsent';     var cookieconsentid = 'cookiechoiceinfo';     var dismisslinkid = 'cookiechoicedismiss';      function _createheaderelement(cookietext, dismisstext, linktext, linkhref) {       var butterbarstyles = 'position:fixed; font: bold 1em \'open sans\', sans-serif; color: white;width:100%;height: 70px;background-color:#666;' +           'margin:0; left:0; top:0;padding:10px;z-index:1000;text-align:center;';        var cookieconsentelement = document.createelement('div');       cookieconsentelement.id = cookieconsentid;       cookieconsentelement.style.csstext = butterbarstyles;       cookieconsentelement.appendchild(_createconsenttext(cookietext));        if (!!linktext && !!linkhref) {         cookieconsentelement.appendchild(_createinformationlink(linktext, linkhref));       }       cookieconsentelement.appendchild(_createdismisslink(dismisstext));       return cookieconsentelement;     }      function _createdialogelement(cookietext, dismisstext, linktext, linkhref) {       var glassstyle = 'position:fixed;width:100%;height:100%;z-index:999;' +           'top:0;left:0;opacity:0.5;filter:alpha(opacity=50);' +           'background-color:#ccc;';       var dialogstyle = 'z-index:1000;position:fixed;left:50%;top:50%';       var contentstyle = 'position:relative;left:-50%;margin-top:-25%;' +           'background-color:#fff;padding:20px;box-shadow:4px 4px 25px #888;';        var cookieconsentelement = document.createelement('div');       cookieconsentelement.id = cookieconsentid;        var glasspanel = document.createelement('div');       glasspanel.style.csstext = glassstyle;        var content = document.createelement('div');       content.style.csstext = contentstyle;        var dialog = document.createelement('div');       dialog.style.csstext = dialogstyle;        var dismisslink = _createdismisslink(dismisstext);       dismisslink.style.display = 'block';       dismisslink.style.textalign = 'right';       dismisslink.style.margintop = '8px';         content.appendchild(_createconsenttext(cookietext));       if (!!linktext && !!linkhref) {         content.appendchild(_createinformationlink(linktext, linkhref));       }       content.appendchild(dismisslink);       dialog.appendchild(content);       cookieconsentelement.appendchild(glasspanel);       cookieconsentelement.appendchild(dialog);       return cookieconsentelement;     }      function _setelementtext(element, text) {       if (supportstextcontent) {         element.textcontent = text;       } else {         element.innertext = text;       }     }      function _createconsenttext(cookietext) {       var consenttext = document.createelement('span');       _setelementtext(consenttext, cookietext);       return consenttext;     }      function _createdismisslink(dismisstext) {       var dismisslink = document.createelement('button');       _setelementtext(dismisslink, dismisstext);       dismisslink.id = dismisslinkid;       dismisslink.style.textdecoration= 'none';       dismisslink.style.color= '#666';       dismisslink.href = '#';       dismisslink.style.marginleft = '24px';       return dismisslink;     }      function _createinformationlink(linktext, linkhref) {       var infolink = document.createelement('a');       _setelementtext(infolink, linktext);       infolink.href = linkhref;       infolink.target = '_blank';       infolink.style.textdecoration= 'none';       infolink.style.color= '#33cc33';       infolink.style.marginleft = '8px';       return infolink;     }      function _dismisslinkclick() {       _saveuserpreference();       _removecookieconsent();       return false;     }      function _showcookieconsent(cookietext, dismisstext, linktext, linkhref, isdialog) {       if (_shoulddisplayconsent()) {         _removecookieconsent();         var consentelement = (isdialog) ?             _createdialogelement(cookietext, dismisstext, linktext, linkhref) :             _createheaderelement(cookietext, dismisstext, linktext, linkhref);         var fragment = document.createdocumentfragment();         fragment.appendchild(consentelement);         document.body.appendchild(fragment.clonenode(true));         document.getelementbyid(dismisslinkid).onclick = _dismisslinkclick;       }     }      function showcookieconsentbar(cookietext, dismisstext, linktext, linkhref) {       _showcookieconsent(cookietext, dismisstext, linktext, linkhref, false);     }      function showcookieconsentdialog(cookietext, dismisstext, linktext, linkhref) {       _showcookieconsent(cookietext, dismisstext, linktext, linkhref, true);     }      function _removecookieconsent() {       var cookiechoiceelement = document.getelementbyid(cookieconsentid);       if (cookiechoiceelement != null) {         cookiechoiceelement.parentnode.removechild(cookiechoiceelement);       }     }      function _saveuserpreference() {       // set cookie expiry 31 days after today.       var expirydate = new date();       expirydate.setdate(expirydate.getdate() + 31);       document.cookie = cookiename + '=y; expires=' + expirydate.togmtstring() +'; path=/;';     }      function _shoulddisplayconsent() {       // display header if cookie has not been set.       return !document.cookie.match(new regexp(cookiename + '=([^;]+)'));     }      var exports = {};     exports.showcookieconsentbar = showcookieconsentbar;     exports.showcookieconsentdialog = showcookieconsentdialog;     return exports;   })();    window.cookiechoices = cookiechoices;   return cookiechoices; })(this);  function delete_cookie(cookie_name) {   var cookie_date = new date ( );     cookie_date.settime ( cookie_date.gettime() - 1 );   document.cookie = cookie_name + '=; path=/; expires=' + cookie_date.togmtstring(); } 

html code:

<a href="#" onclick="delete_cookie('displaycookieconsent');" class="">clicca qui per cancellarlo</a>