javascript[js]获取url参数

<script language=javascript>  
    function request(paras) {
        var url = location.href;
        var paraString = url.substring(url.indexOf("?") + 1, url.length).split("&");
        var paraObj = {}
        for (i = 0; j = paraString[i]; i++) {
            paraObj[j.substring(0, j.indexOf("=")).toLowerCase()] = j.substring(j.indexOf("=") + 1, j.length);
        }
        var returnValue = paraObj[paras.toLowerCase()];
        if (typeof(returnValue) == "undefined") {
            return "";
        } else {
            return returnValue;
        }
    }
    var theurl = request('url');
    var theimg = request('img');
    document.writeln("<a href='" + theurl + "' target=_blank><img src=" + theimg + " width=750 height=450 border=0></a>");
</script>