How to get a URL parameter in Express?

How to get a URL parameter in Express?

I am facing an issue on getting the value of tagid from my URL: localhost:8888/p?tagid=1234.
Help me out to correct my controller code. I am not able to get the tagid value.
My code is as follows:
app.js:
var express = require(‘express’),
http = require(‘http’),
path = require(‘path’);
var app = express();
var controller = require(‘./controller’)({
app: app
});

// all environments
app.configure(function() {
app.set(‘port’, process.env.PORT || 8888);
app.use(express.json());
app.use(express.urlencoded());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, ‘public’)));
app.set(‘view engine’, ‘jade’);
app.set(‘views’, __dirname + ‘/views’);
app.use(app.router);
app.get(‘/’, function(req, res) {
res.render(‘index’);
});
});
http.createServer(app).listen(app.get(‘port’), function() {
console.log(‘Express server listening on port ‘ + app.get(‘port’));
});

Controller/index.js:
function controller(params) {
var app = params.app;
//var query_string = request.query.query_string;

app.get(‘/p?tagId=/’, function(request, response) {
// userId is a parameter in the url request
response.writeHead(200); // return 200 HTTP OK status
response.end(‘You are looking for tagId’ + request.route.query.tagId);
});
}

module.exports = controller;

routes/index.js:
require(‘./controllers’);
/*
* GET home page.
*/

exports.index = function(req, res) {
res.render(‘index’, {
title: ‘Express’
});
};

Solutions/Answers:

Solution 1:

Express 4.x

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To get a URL parameter’s value, use req.params

app.get('/p/:tagId', function(req, res) {
  res.send("tagId is set to " + req.params.tagId);
});

// GET /p/5
// tagId is set to 5

If you want to get a query parameter ?tagId=5, then use req.query

app.get('/p', function(req, res) {
  res.send("tagId is set to " + req.query.tagId);
});

// GET /p?tagId=5
// tagId is set to 5

Express 3.x

URL parameter

app.get('/p/:tagId', function(req, res) {
  res.send("tagId is set to " + req.param("tagId"));
});

// GET /p/5
// tagId is set to 5

Query parameter

app.get('/p', function(req, res) {
  res.send("tagId is set to " + req.query("tagId"));
});

// GET /p?tagId=5
// tagId is set to 5

Solution 2:

You can do something like req.param('tagId')

Solution 3:

If you want to grab the query parameter value in the URL, follow below code pieces

//url.localhost:8888/p?tagid=1234
req.query.tagid
OR
req.param.tagid

If you want to grab the URL parameter using Express param function

Express param function to grab a specific parameter. This is considered middleware and will run before the route is called.

This can be used for validations or grabbing important information about item.

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An example for this would be:

// parameter middleware that will run before the next routes
app.param('tagid', function(req, res, next, tagid) {

// check if the tagid exists
// do some validations
// add something to the tagid
var modified = tagid+ '123';

// save name to the request
req.tagid= modified;

next();
});

// http://localhost:8080/api/tags/98
app.get('/api/tags/:tagid', function(req, res) {
// the tagid was found and is available in req.tagid
res.send('New tag id ' + req.tagid+ '!');
});

Solution 4:

This will work if your route looks like this: localhost:8888/p?tagid=1234

var tagId = req.query.tagid;
console.log(tagId); // outputs: 1234
console.log(req.query.tagid); // outputs: 1234

Otherwise use the following code if your route looks like this: localhost:8888/p/1234

var tagId = req.params.tagid;
console.log(tagId); // outputs: 1234
console.log(req.params.tagid); // outputs: 1234