直接上方法了

'https://old.xhcss.com/xh/dedecms/mark/'.replace(/^https?:\/\/[^/]+/, ""); // => /xh/dedecms/mark/
'https://old.xhcss.com/xh/dedecms/mark/'.replace(/^https?:\/\/[^/]+\//, "");// => xh/dedecms/mark/'