如何访问Express.js中的可选URL参数？

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?

Answer 1

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}

Answer 2

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.