//为url字符串添加、修改参数

String.prototype.EditUrlParam = function (paramName, replaceWith) {

    var url = this;

    if (url.indexOf(paramName) > -1) {

        var re = eval('/(' + paramName + '=)([^&]*)/gi');

        url = url.replace(re, paramName + '=' + replaceWith);

    } else {

        var paraStr = paramName + '=' + replaceWith;

        var idx = url.indexOf('?');

        if (idx < 0)

            url += '?';

        else if (idx >= 0 && idx != url.length - 1)

            url += '&';

        url=url + paraStr;

    }

    return url;

};