var url = require('url');

 var a = url.resolve('/one/two/three', 'four') ,

 b = url.resolve('http://example.com/', '/one'),

 c = url.resolve('http://example.com/one', '/two');

 console.log(a +","+ b +","+ c);

 //输出结果：

 ///one/two/four

 //http://example.com/one

 //http://example.com/two