js获取url参数值的方式

function getParam(paramName) {
    paramValue = "";
    isFound = false;
    paramName = paramName.toLowerCase();
    var arrSource = this.location.search.substring(1, this.location.search.length).split("&");
    if (this.location.search.indexOf("?") == 0 && this.location.search.indexOf("=") > 1) {
        if (paramName == "returnurl") {
            var retIndex = this.location.search.toLowerCase().indexOf(‘returnurl=‘);
            if (retIndex > -1) {
                var returnUrl = decodeURIComponent(this.location.search.substring(retIndex + 10, this.location.search.length));
                if ((returnUrl.indexOf("http") != 0) && returnUrl != "" && returnUrl.indexOf(location.host.toLowerCase()) == 0) returnUrl = document.location.protocol + "//" + returnUrl;
                return returnUrl;
            }
        }
        i = 0;
        while (i < arrSource.length && !isFound) {
            if (arrSource[i].indexOf("=") > 0) {
                if (arrSource[i].split("=")[0].toLowerCase() == paramName.toLowerCase()) {
                    paramValue = arrSource[i].toLowerCase().split(paramName + "=")[1];
                    paramValue = arrSource[i].substr(paramName.length + 1, paramValue.length);
                    isFound = true;
                }
            }
            i++;
        }
    }
    return paramValue;
}