Node.js + Append to model before rendering a view

I am building a website using Node.js and Express. For my view engine, I'm using Vash.

In my app, I have a layout.vash file I'm using as the main layout for my app. It looks something like this:

layout.vash

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>@model.title</title>
  </head>
  <body>
    @html.block('content')
  </body>
</html>

I then have views that look something like this:

view.vash

@html.extend('layout', function(model){
    @html.block('content', function(model){
      <h1>Hello</h1>
    })
})

The view is referenced via Express with a route similar to this:

var router = require('express').Router();
router.get('/', function(req, res) {
    var viewModel = {
      title: 'Hello'
    };

    res.render('view', viewModel);
});

My viewModel will be unique to each view. However, there are some properties that are shared across all views. For example, for development purposes, I would like to know if the request is local or not. If I was using ASP.NET, I know I could say:

@if (Request.IsLocal) { ... }

However, I'm not sure how to do something similar with Node and Vash. My instincts tell me that I somehow need to append a property called isLocal to my model. However, I'm not sure if that's the correct idea, or if that's even possible.

Solution

I use the approach you are considering in my personal code.

If the values you want to attach to your model are common across multiple routes, consider using a function to extend your model:

function appendRouteData(model) {
    model.routes = {};
    model.routes.controller = "SomeController";
    model.routes.action = "index";
    model.routes.parameters = { foo: "bar" };
    return model;
}

...

viewModel = appendRouteData(viewModel);

In response to your comments, there are multiple ways to include such a function in your users.js.

Either expose the method as another module and require it, or, if we're going full crazy, inject a function that performs the same, but this requires some refactoring. I anticipate you doing only some of this insanity...

// routes.js
var UserRoutes = require('./users');
function appendRouteData(controllerName) {
    // some crazy javascript here, might want to contemplate how this actually works first.
    return function (viewModel) {
        viewModel.routes.controller = controllerName;
        return viewModel;
    };
}

module.exports = {
    users: UserRoutes(appendRouteData('users'))
};

// users.js
function UserRoutes(appendRouteData) {
    var router = require('express').Router();
    router.get('/users', function (req, res) {
        var viewModel = {};
        viewModel = appendRouterData(viewModel);
        res.render('users/index', viewModel);
    });
    return router;
}
module.exports = UserRoutes;