how to req.params as string code example

Example 1: req.params req.query

req.params contains route parameters (in the path portion of the URL), 
and req.query contains the URL query parameters (after the ? in the URL).

You can also use req.param(name) to look up a parameter in both places (as well as req.body),

Example 2: req.params

params. An object containing parameter values parsed from the URL path. For example if you have the route /user/:name , then the "name" from the URL path wil be available as req.params.name .