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Regex Routes in Express.js

Express.js support regex routing with simplified string based rules, custom regex rules for specific parameters, and pure regex rules to match and entire route.

If you want to use regex for an Express.js route rule then you must use a JS regular expression object instead if string by wrapping your regular expression in slashes (/) instead of quotes ("). To look at a common usage example, let’s say you want the same route handler for two different root paths in your app, like /rest/* and /api/*.

String Routing Rules

Express uses path-to-regexp to simplify the process of writing routing rules. path-to-regex is what turns rules like /order/:id or /post/:id into a RegEx pattern for matching.

// String route rules
var handler = function( req, res, next ) {
    res.send( "My route worked!" );
};
app.get( '/api/:param', handler );
app.get( '/rest/:param', handler );

Regex Rules for Parameters

Express.js provides a way to use a custom regex rule for a specific parameter in a route. Let’s say we wanted a :userId parameter in a route rule to match only a 6 digit integer. The following regex parameter rule does that well.

// Regex rule for route parameter
app.get( '^/users/:userId([0-9]{6})', function( req, res ) {
    res.send( 'Route match for User ID: ' + req.params.userId );
} );

Pure Regex Routing Rules

If you want to use a pure regex for an Express.js route rule then you must use a JS regular expression object instead if string by wrapping your regular expression in slashes (/) instead of quotes (").

// Regex route rule
app.get( /^\/(api|rest)\/.+$/, function( req, res, next ) {
    res.send( "My route worked!" );
} );

Helpful Tools

If you’re writing custom regex routing rules for Express.js then I highly suggest the following useful tools:

  • Express Route Tester — A great utility that you can use to test out how Express routes are translated to regex rules
  • Regex101 — A great resource for creating, testing, and understanding regular expressions
  • Express.js Routing Docs — Be sure to reference these for basics on Express.js routing

Meet the Author

Kevin Leary, WordPress Consultant

I'm a freelance web developer and WordPress consultant in Boston, MA with 15 years of experience building websites and applications. View a portfolio of my work or request an estimate for your next project.