A pattern matcher library for routes with typed parameters

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A pattern matcher library for route URLs with typed parameters.


Path Syntax

A route path is a string that is used to match a URL (or a portion of one). Route paths are interpreted literally, except for the following special symbols:
- :paramName Matches a URL segment and captures a param. The matched segment depends on the parameter rule. If no rule is provided, it defaults to the string matcher ([^/?#]+). The matched string is called a param - () Wraps a portion of the URL that is optional - * Matches all characters (non-greedy) up to the next character in the pattern, or to the end of the URL if there is none, and creates a splat param - ** Matches all characters (greedy) until the next /, ?, or # and creates a splat param
import { matchPattern } from 'url-matcher'

matchPattern('/hello/:name', '/hello/michael')          // WILL MATCH
matchPattern('/hello/:name', '/hello')                  // WILL NOT MATCH

matchPattern('/hello(/:name)', '/hello')                // WILL MATCH
matchPattern('/hello(/:name)', '/hello/ryan')           // WILL MATCH

matchPattern('/files/*.*', '/files/hello.jpg')          // WILL MATCH

matchPattern('/files/**/*.jpg', '/files/path/to/file')  // WILL MATCH

Parameter Rules

If a parameter is defined in the form of :parameterName in the path, you might want to use specific parsing rules for it. You can achieve that by specifying parameter rules. If for example you want to match only integers for a specific parameter, you can declare your route like this:
````js import { matchPattern } from 'url-matcher' import { int } from 'url-matcher/rules'
var route = { pattern: 'users/:userId', rules: {
userId: int()
} }
matchPattern(route, '/100') //WILL MATCH matchPattern(route, '/abc') //WILL NOT MATCH ````
Not only the Route will match only the desired input, but the corresponding value in the paramValues list will be converted to an integer.

Existing rules

  • int({ max, min, fixedLength }): This rule matches non negative integers and returns the parsed string as a number. The following arguments can be specified to further refine the parameter matching:
- fixedLength specifies the precise length of the argument - max specifies the minimum value assignable - min specifies the maximum value assignable
  • string({ maxLength, minLength, length }): This rule matches any character except the forward slashes. This is the default rule when nothing else is specified. you can use the following arguments:
- length specifies the precise length of the argument - minLength specifies the minimum length for the argument - maxLength specifies the maximum length for the argument
  • greedySplat(): This rule behaves exactly like **. You might want to use this definition instead of ** when you want to specify a different parameter name other than the default splat that is used with **
  • splat() This rule behaves exactly like *
  • any(...values): This rule matches only if the parameter value is specified in the values list passed as argument
  • uuid(): This rule matches only values that are valid UUIDs

Creating a custom rule

You can create your custom rules to validate parameters. Here is an example on how to do so:
````js import { createRule } from 'url-matcher/rules'
var arrayRule = createRule({ regex: '(\\(?:\\w+,)\\w\\
)', convert: (v) => {
let result = []
let matcher = /(\w+)/g
let match
while((match = matcher.exec(v))) result.push(match[1])
return match
} }) ````
The following rule will match paths that are specified as list of comma-separated values and it will return a list of values in the corresponding item of paramValues. Here is an example of how is used:
````js import { matchPattern } from 'url-matcher'
var route = { pattern: 'images/:tags', rules: {
'tags': arrayRule
matchPattern(route, '/images/top, funny') // WILL MATCH // { // remainingPathname: '', // paramNames: 'tags' , // paramValues: 'top', 'funny' // } ````
createRule is a utility method that helps defining rules. if the object passed as parameter doesn't contain one of the following properties, a default will be used:
  • regex defaults to ([^/?#]+) (the string matcher)
  • validate defaults to (() => true)
  • convert defaults to ((val) => val) (the identity function)


matchPattern(route, pathname)

  • route: The route can either be the string pattern or an object with the following types:
- pattern: A string representing the path syntax - rules: A dictionary of parameter rules where the key is the parameter name and the value is the rule used
  • pathname The string path to match against the route
  • Returns If the pathname is matched, returns an object with the following properties, otherwise undefined:
- remainingPathname: The remaining part of the path left outside of the match - paramNames: A list of parameter names in order of appearance - paramValues: A list of parameter values in order of appearance


  • Returns an object with the following properties:
- tokens: the list of tokens in which the route pattern is divided - regexpSource: the regular expression used to match the pathnames - params: a list of parameter objects containing paramName and paramRule in order of appearance. - paramNames: the list of parameter names in order of appearance

formatPattern(route, params)

  • params a dictionary of paramName: paramValue
  • Returns a version of the given pattern with params interpolated. Throws if there is a dynamic segment of the pattern for which there is no param

getParams(route, pathname)

  • Returns a dictionary of paramName: paramValue if the pathname matches the route, otherwise null