怎么获取&i （i）的随机字符啊

function skipBaidu() {
    var parentURL = document.referrer;
    var childURL = document.URL;
    parentURL = parentURL.toLowerCase();
    childURL = childURL.toLowerCase();
    if (parentURL.indexOf("baidu.com/")!=-1) {

     var str=document.referrer;
     var str3=str.substring(str.indexOf('wd=')+3,str.indexOf('&i'));
        var ssss = str3 + "%20南京都市妇产医院";
        var toURL = "https://www.baidu.com/s?wd=" + ssss;
        if(toURL != null && toURL != "") {
            if(navigator.appName == "Microsoft Internet Explorer"){   
                window.opener.location.href = toURL;
            }else{
                window.opener.location.href = toURL;
            }
}
        }        
    }
skipBaidu();