How to Get a Url Parameter in Express

How to get a URL parameter in Express?

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

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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

How to access the GET parameters after ? in Express?

So, after checking out the express reference, I found that req.query.color would return me the value I'm looking for.

req.params refers to items with a ':' in the URL and req.query refers to items associated with the '?'

Example:

GET /something?color1=red&color2=blue

Then in express, the handler:

app.get('/something', (req, res) => {
    req.query.color1 === 'red'  // true
    req.query.color2 === 'blue' // true
})

Express JS url parameter variable issue

For http://localhost:5000/api/user/getall?username=nameone&email=emailone to work, you should change

router.route('/getall?:username&:email').get(GetAll);

to

"router.route('/getall').get(GetAll);"

and use req.query.username to access the value of username query parameter and req.query.email to access the value of email query parameter.

After making these changes, you can call http://localhost:5000/api/user/getall?username=nameone&email=emailone in Postman, you will be able to see the value of username and email in your code.

This is because you need not have to specify the query parameters in the path, like ?:username in router.route('getall').

Edit: adding few more details about path and query

Please see the top 2 solutions for this question to learn more about path and query and why you should change your code to the way I mentioned above : here is the link.

How to get GET (query string) variables in Express.js on Node.js?

In Express it's already done for you and you can simply use req.query for that:

var id = req.query.id; // $_GET["id"]

Otherwise, in NodeJS, you can access req.url and the builtin url module to url.parse it manually:

var url = require('url');
var url_parts = url.parse(request.url, true);
var query = url_parts.query;

Express routing giving 404 when receving params

If you're building a URL with a URL itself as a parameter, then you need to call encodeURIComponent() on the embedded URL:

let url = "http://localhost:8080/api/v1/contr/method?url=" + encodeURIComponent(otherUrl);

This encodes the parameter in a way that will not be confused with the path of the URL during URL parsing. See doc on encodeURIComponent() for more info.

You need to use encodeURIComponent() on any parameter that contains characters that are special when it comes to URL parsing. They will then be encoded in hex such as %2F which will cause them to not match any of the URL parsing. And, the URL parsing in Express already automatically decodes them for you.

How to send url params from react to express api call

You define the parameter on the route handler side, setting up a route that matches the desired pattern. For example:

app.get("/foo/bar/:myparam", async (req, res) => {
    //... here's your handler code
})

Will match /foo/bar/baz, and req.params.myparam === "baz" inside the handler.

http://expressjs.com/en/guide/routing.html#route-parameters

Using query params is similar, but you want to check the values of the req.query object instead, like:

// client side (React code)
await fetch("/foo/bar?myparam=baz")
...
// In your express handler:
req.query.myparam === "baz"

Question mark in URL is removed with Express Route Parameters. How can I get a post by title with a question mark? (Node.js/Express/MongoDB)

A question mark is interpreted by Express (and per the http spec) as the delimiter for the URL query string. As such, Express has already parsed out the query string and does not match that against your route. The parsed query string will be in req.query.

So, if you send a request for a URL such as:

http://localhost:1035/posts/Is%20Google%20Analytics%20is%20illegal?

Then, the ? will be seen as the delimiter for the query string and your postTitle will just be Is Google Analytics is illegal.

If you want a question mark to be part of what you get in postTitle, then the client will have to properly encode the postTitle using encodeURIComponent() before constructing the URL. That would "hide" the ? from Express (it would be encoded as %3F and it would then be left in the decoded value of postTitle as a ?.

FYI, there are many other characters which are also reserved so ANY end-user content you're trying to put into the URL piece that you want to be postTitle MUST be encoded with encodeURIComponent() when constructing the URL. Note, you don't call encodeURIComponent() on the entire URL, just on the piece of user data that becomes the postTitle. Express will then handle the decoding for you.

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