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'
});
};
/p?tagid=1234, tagid is called a query string, not a URL parameter. A URL parameter would be /p/:tagId.
Express 4.x
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
You can do something like req.param('tagId')
req.query and req.params is so different things, the replacement for req.param('x') is req.params.x not req.query.
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.
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+ '!');
});
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
/p/:tagid=1234
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express-3.4.4and it works fine./p/5if you're using the top solution, or/p?tagId=5if you're using the bottom solution.req.param()is deprecated:Use either req.params, req.body or req.query, as applicable.For named route "parameters" (e.g./p/:tagId) usereq.params. For query strings (e.g./p?tagId=5) usereq.query.