How to access optional URL parameters in Express.js?

Question

In Express.js 4.14, I have the following route:

app.get('/show/:name/:surname?/:address?/:id/:phone?', function(req, res) {
    res.json({
        name: req.params.name,
        surname: req.params.surname,
        address: req.params.address,
        id: req.params.id,
        phone: req.params.phone
    });
});

If I request localhost:3000/show/luis/arriojas/California/123/456, I will receive:

{"name":"luis","surname":"arriojas","address":"California","id":"123","phone":"456"}

Everything is OK with that, but if I request localhost:3000/show/luis/California/123, I will receive:

{"name":"luis","surname":"California","id":"123"}

How could I get "California" as req.params.address instead of req.params.surname?

That is impossible to know... There is no difference between the state and the name. — epascarello
– epascarello, Commented Jul 6, 2016 at 20:01

Emilio Platzer · Accepted Answer · 2016-07-06 20:06:25Z

16

app.get('/show/:name/:id/', function(req, res) {
    res.json({
        name: req.params.name,
        surname: req.query.surname,
        address: req.query.address,
        id: req.params.id,
        phone: req.query.phone
    });
});

If I you request localhost:3000/show/luis/123?surname=arriojas&address=California&phone=456, you will receive:

{"name":"luis","surname":"arriojas","address":"California","id":"123","phone":"456"}

and if you request localhost:3000/show/luis/123&address=California, you will receive:

{"name":"luis","surname":undefined, "address":"California","id":"123","phone":undefined}

answered Jul 6, 2016 at 20:06

Emilio Platzer

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1 Comment

Luis Arriojas Over a year ago

Thanks Emilio. It works like a tango, simply beautiful.

d_shiv · Accepted Answer · 2016-07-06 20:15:54Z

You have multiple consecutive optional parameters in your URL. When you hit localhost:3000/show/luis/California/123, express had no way of knowing which parameters you intended to skip, and which to keep. It ended up assigning parameters left to right, skipping assignment of the last unsatisfiable optional parameter.

To solve this issue, you can either change your program design to accept all the parameters as query string instead of url parameter. In which case you'd access your API with 'localhost:3000/show?name=luis&address=California&id=123', and your code you be like:

app.get('/show', function(req, res) {
    res.json({
        name: req.query.name,
        surname: req.query.surname,
        address: req.query.address,
        id: req.query.id,
        phone: req.query.phone
    });
});

However, if you want to use url parameters, you will have to insert a mandatory path component between optional components. Something like,

app.get('/show/:name/:surname?/at/:address?/:id/:phone?', function(req, res) {

Now you would access your API as 'localhost:3000/show/luis/at/California/123'. Here, by knowing position of 'at' in url, express would correctly assign 'California' to address instead of surname.

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