To get all routes registered in express.js, this snippet gets the work done:

const routes = [];

app._router.stack.forEach((middleware) => {
  if (middleware.route) {
    routes.push(
      `${Object.keys(middleware.route.methods)} -> ${middleware.route.path}`
    );
  }
});

console.log(JSON.stringify(routes, null, 2));

Possible result:

[
  "post -> /customers"
  "put -> /customers/:id",
  "delete -> /customers/:id"
]