Express middleware access to req.params

Question

I'd like to isolate a piece of code that would inspect either req.params or req.body for a value that is required on every request. What I'm finding is that if I try to access those values before app.use(app.router) then the request hasn't been parsed to include those objects. If I try to insert the middleware after app.use(app.router) then it gets skipped all together.

What can I do to work on these values in one place so that the work is ready to be used by downstream routes and models?

Answer 1

Just run the middleware inline with each route,

const middleware = (req, res, next) => {
    console.log(req.params.id);
    next();
};

app.get('/test/:id', middleware, (req, res) => {
    res.send('hi');
});

Answer 2

You cannot do what you are trying to do. https://github.com/strongloop/express/issues/2088 explains this very clearly.

I have been trying to do what you are trying to do for some time, with no success. I finally tracked down this issue in github.

Answer 3

Since my original answer won't obtain route parameters from the URL, e.g. /things/:foo (although it will get querystring and req.body params), it won't work the way we want. But another option would be to write a wrapper function that does what you need, and apply it to your route middleware:

function checkForParam (fn) {

    return function(req, res, next) {

       if (req.param('foo') != 'bar') {
          return res.send(403, 'No way Jose!');
       }

       fn (req, res, next);

    };

}

Then add routes with:

app.get('/things/:foo', checkForParam(function(req, res, next) {
  // your middleware code here
});

This will run the check and proceed to your custom route middleware only if it passes muster.

Answer 4

I like this way:

const controller = function (name, method) {
  return function (req, res) {
    // COERCE ID
    if (req.method === 'GET' || req.method === 'DELETE') {
      var _id = req.params && req.params._id || false
      if (/^[0-9a-f]{24}$/.test(_id)) {
        req.params._id = new ObjectID(_id)
      }
      else if (_id) {
        return res.status(404).send('Page not found.')
      }
    }
    require('./api/' + name + '.js')[method](req, res)
  }
}

Then:

app.get('/api/post/:_id', controller('posts', 'get'))

Answer 5

Tried a simple core level workaround to get the URL params in router before proceeding into router

I need to validate the URL param id where it is an project id and to check respective user has access to it or not

And i don't want to use it in all routes as middleware so used split function to extract the project id which is in URL params

  router.use(apiauthenticated,(req,res,next)=>{
     try {  
          //req.params.projectid  
          let temp_projectid=req.originalUrl.split("/") //Getting all endpoints and params
          let last_element=temp_envid[temp_envid.length-1] //Get last element from array for URL params
          let projectid =last_element.includes("?") ? last_element.split("?")[0] : last_element //Returning URL params with or without query params
          if(projectid === "" ){
             //if it is null throwing error
             throw "Please provide required  projectid";
          }
          //Db validation here with projectid
          next();     
        } catch (error) {
            res.status(400).send(error);
            return null;
        }     
  })

apiauthenticated is the middleware to validate the API Key

Used last_element.includes("?") ? last_element.split("?")[0] : last_element for handling the query params