config.json

[
    {
        "path": "/todo/list",
        "handler": "ListHandler",
        "verb": "get"
    },
    {
        "path": "/todo/list/:id",
        "handler": "DetailHandler",
        "verb": "get"
    }
]

dynamic-express-app.js

var express = require('express');
var app = express();

// load config from file
var config = require('config.json');

// handler mappings
var handlers = {
    'ListHandler': require('list-handler'), // different request handlers in different modules
    'DetailHandler': require('detail-handler')
};

config.forEach((route) => {
    // lookup the request handler from the handler mapping above so different paths can call different handlers.
    let routeHandler = handlers[route.handler];
    
    // now set up a route at the path defined in the config pointing to the handler
    app[route.verb](route.path, routeHandler);
});