js替换url里面的变量

  function replaceParamVal(paramName,replaceWith) {
            var oUrl = this.location.href.toString();
            var re=eval('/('+ paramName+'=)([^&]*)/gi');
        if (re.test(oUrl)){
        var nUrl = oUrl.replace(re,paramName+'='+replaceWith);
        }else{
        if(oUrl.indexOf('?')>0){
        var nUrl = oUrl+"&"+paramName+"="+replaceWith;
        }else{
        var nUrl = oUrl+"?"+paramName+"="+replaceWith;
        }
        }
            this.location=nUrl;
        }