Is the Regex right against what am I trying to do?

Question

Is the Regex right against what am I trying to do?

I am creating a reusable node.js NavigationController class so I can reuse this in other server side projects If I may need or someone else may find it useful.

Here's the use case.

var navController = new NavigationController({
    routes : {
        '/user/:action/:anything' : 'UserController',
        '/app/:action' : 'AppController',
        '/file/:action' : 'FileController',
        '/feedback/:action' : 'FeedbackController',
        '/:anything' : 'ErrorController'
    },
    ErrorController : 'ErrorController'
});
navController.init();

The user upon server request can call this function of that object.

navController.navigate(req, res);

Now this and controllers are being called rightly. The thing under navigate(req, res) function which is a part of calling appropriate controller object based on URL is defined as function named getRouteByPath(path). This private function will get the route and will allow navigate(req, res) function to get controller class name to call.

var getRouteByPath = function(path) {
    for(var route in config.routes) {
        var routeRegex = '';

        var routeParts = route.split('/');

        for(var rp = 0; rp < routeParts.length; rp++) {

            // checking if route part starts with :
            if(routeParts[rp].indexOf(':') === 0) {

                // this is "anything" part
                routeRegex += '[/]?([A-Za-z0-9]*)';

            } else if(routeParts[rp] != "") {
                routeRegex += '[/]?' + routeParts[rp];
            }
        }

        var routeRegexResult = path.match(routeRegex);
        if(routeRegexResult) {
            console.log(routeRegexResult);
            return route;
        }
    }
    return null;
};

I am too worried about this function as if this is the right way to do that?

javascript
regex
node.js
webserver

Answer 1

Some flaws:

Why do you use the slash as a character class ([/])? No need to do that, only in regex literals you'd need to escape it with a backslash (like /\//g). Just use a single "/" instead (new RegExp("/", "g")).
.indexOf(<string>)==0 does work, but searches the whole string and is not very efficient. Better use startswith, in your case routePart.charAt(0)==":"
<string>.match(<string>) - I recommend building a new RegExp object and use .test, as you don't want to match - there is also no need to build capturing groups, I think, because you only return the route string but no matches (okay, you log them).
You want to check if the whole path matches your regexp? Dont forget to add ^ and $. Your current regex for the AppController also matches a route like /user/app/example.
Why is your slash (and only the slash) optional (/?)? Not only I don't think this is what you want, but it also opens the doors to catastrophic backtracking when building regexes like /\/?user\/?([A-Za-z0-9]*)\/?([A-Za-z0-9]*)/

To escape that, you would need to make the whole group optional: (?:/([^/]*))?.
Also, you should build the regexes only once (on initialisation) and store them in a cache, instead of building them each time you call getRouteByPath. The compilation of the RegExp is somewhere hidden in your code, although it needs to happen.

Answer 2

A few notes:

routeRegex += '[/]?([A-Za-z0-9]*)';

says the routes may or may not be present // will match maybe a + is more suited than a *.

Also since I thin _ is allowed in a web route

Your .split('/'), will remove all / from the route so it shouldn't be in split list