點擊某鏈接前判斷用戶是否登錄

若登陸，則直接跳轉

若未登錄，則提醒用戶登錄

<a href="javascript:;" onclick="focusLink('${url}')" style="cursor: pointer">

function focusLink(url){
    var userId = $("#userId_hidden").val();
    if(userId.length == 0){
        window.scrollTo(0,document.body.scrollHeight*0.08);
        $("#username").focus();
        return;
    }
    window.open(url);
}