求帮忙把一个C#正则弄成一个js正则。该怎么解决

求帮忙把一个C#正则弄成一个js正则。

C# code

String regex = @"(\bitem_num_id\b|\bitem_num\b|\bmallstItemId\b|\bdefault_item_id\b|\bid\b)=([\d]+)";var res = Regex.Match(url, regex, RegexOptions.Singleline | RegexOptions.IgnoreCase)                .Groups;

JScript code

var reg=/(\bitem_num_id\b|\bitem_num\b|\bmallstItemId\b|\bdefault_item_id\b|\bid\b)=([\d]+)/i;var res=url.match(reg).length;