# Routes' Matching Syntax

Most applications will use static routes like /about and dynamic routes like /users/:userId like we just saw in Dynamic Route Matching, but Vue Router has much more to offer!

# Custom Regexp in params

When defining a param like :userId, we internally use the following regexp ([^/]+) (at least one character that isn't a slash /) to extract params from URLs. This works well unless you need to differentiate two routes based on the param content. Imagine two routes /:orderId and /:productName, both would match the exact same URLs, so we need a way to differentiate them. The easiest way would be to add a static section to the path that differentiates them:

const routes = [
  // matches /o/3549
  { path: '/o/:orderId' },
  // matches /p/books
  { path: '/p/:productName' },
]

But in some scenarios we don't want to add that static section /o/p. However, orderId is always a number while productName can be anything, so we can specify a custom regexp for a param in parentheses:

const routes = [
  // /:orderId -> matches only numbers
  { path: '/:orderId(\\d+)' },
  // /:productName -> matches anything else
  { path: '/:productName' },
]

Now, going to /25 will match /:orderId while going to anything else will match /:productName. The order of the routes array doesn't even matter!

# Repeatable params

If you need to match routes with multiple sections like /first/second/third, you should mark a param as repeatable with * (0 or more) and + (1 or more):

const routes = [
  // /:chapters -> matches /one, /one/two, /one/two/three, etc
  { path: '/:chapters+' },
  // /:chapters -> matches /, /one, /one/two, /one/two/three, etc
  { path: '/:chapters*' },
]

This will give you an array of params instead of a string and will also require you to pass an array when using named routes:

// given { path: '/:chapters*', name: 'chapters' },
router.resolve({ name: 'chapters', params: { chapters: [] } }).href
// produces /
router.resolve({ name: 'chapters', params: { chapters: ['a', 'b'] } }).href
// produces /a/b

// given { path: '/:chapters+', name: 'chapters' },
router.resolve({ name: 'chapters', params: { chapters: [] } }).href
// throws an Error because `chapters` is empty

These can also be combined with custom Regexp by adding them after the closing parentheses:

const routes = [
  // only match numbers
  // matches /1, /1/2, etc
  { path: '/:chapters(\\d+)+' },
  // matches /, /1, /1/2, etc
  { path: '/:chapters(\\d+)*' },
]

# Optional parameters

You can also mark a parameter as optional by using the ? modifier (0 or 1):

const routes = [
  // will match /users and /users/posva
  { path: '/users/:userId?' },
  // will match /users and /users/42
  { path: '/users/:userId(\\d+)?' },
]

Note that * technically also marks a parameter as optional but ? parameters cannot be repeated.

# Debugging

If you need to dig how your routes are transformed into Regexp to understand why a route isn't being matched or, to report a bug, you can use the path ranker tool. It supports sharing your routes through the URL.